So ya got yourself a fish tank, and now you're wondering how to cycle it.
You have a few options:
1) Fishless cycle: Set up your substrate and filter (decorations and plants are optional), buy pure ammonia, add enough to your tank to read 3ppm, wait. Full instructions here: https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/
2) Planted/Silent cycle: the focus of this article
3) Fish-in cycle: set up your tank, add 1-3 fish, test ammonia and nitrites daily, do 75%+ water changes daily until ammonia and nitrites go to zero, and pray that your fish don't die. Additional instructions here: https://www.fishforums.net/threads/rescuing-a-fish-in-cycle-gone-wild-part-i.433769/
Which option is best for you? Depends on your personality and experience level, as well as how much work and stress you want. (hint:: option #3 is the most stressful and labor intensive). If you like chemistry and measuring things, and don't want to mess with plants, then option 1 is probably a great fit for you. If you want to get your hands wet right away, and don't mind some stuff floating around your tank for a couple of months until things stabilize, then option 2 may be worth considering! For the sake of the fish, don't do option 3 as your first choice. Options 1 and 2 are more ethical approaches to cycling a tank.
Please note, that with both a planted/silent cycle and a fish-in cycle, inhabitants must be added gradually (no more than 1-3 at a time) to the tank. If you want to take an approach where you get most of your fish in one fell swoop (if you are ordering stock online for example) then a fishless cycle is recommended.
The rest of this article focuses on how to do a Planted/Silent cycle. Credit for all of this knowledge goes to the wonderful people on this forum, without which I could not have compiled any of this information! A special thank you especially to @Essjay, who proofread this upteen times
To set up a planted/silent cycle, do the following:
1) leak test your aquarium
2) wash and place the substrate, filter, heater, thermometer, light(s) and any other hardware you wish to add. Fill up your tank, and add water conditioner/dechlorinator if your water requires it. I suppose this is technically optional with no inhabitants, but you're going to need it anyway in the future so might as well get in the habit.
3) acquire many fast-growing plants, in addition to any other plants you may wish to include in your aquascape at this point. The fast-growing plants are ideally ones that feed directly from the water column. You are not obligated to keep the fast-growing plants forever, but for the purposes of getting your tank cycled and your fish added, be prepared to have the plants in there for 3-6 months. You should aim to have at LEAST 30% of your water VOLUME filled with plant matter.
Examples of plants that are good to use for a planted/silent cycle are:
Hornwort
Elodea / anacharis / water weed / pond weed: actually a family of plants, but most of them work relatively well. One common example: look for "egeria densa" (also called elodea densa)
Frogbit
Duckweed (note, this may be difficult to get rid of due to its small size, but will not do well in a high current.)
Water sprite / water wisteria (similar plants, but water sprite may be slightly better suited due to its preference for leaf feeding, but both are fast-growing plants)
Because many of these plants are fast growing, they are also considered invasive and may be illegal in specific areas. Please check with your local authority before buying these plants online to determine whether they are considered invasive. To dispose of the plants listed above, please boil or fully dry them before placing them in the TRASH or deep into a compost heap (not down the drain or near any other water source). Many of these plant species will propagate from a tiny fraction of a leaf, which is why they pose a risk of being invasive.
4) Take a picture of your tank to document how big the plants are. Set your lights on a timer so that the plants get 6-10h of light (depending on then intensity of your particular light bulb. If you start to get algae, give less light).
5) (optional) add root tabs or liquid fertilizers (as appropriate for the plants you have - the plants listed above do not need root tabs) to your tank. This will help speed up the plant growth in the absence of fish waste.
6) go do something else with your life for a while, and two weeks later, compare your photo to the present situation. If there is significant growth, your silent cycle could be complete!
7) Once your cycle is complete, fish should be added gradually and slowly. Unless your goal is a Walstad-style tank, your inhabitants may ultimately produce more ammonia than what your plants will ever be able to handle (this largely depends on the plant species in your tank), which is why you need to allow time for the beneficial bacteria to establish themselves in your tank in the background (the "silent" part of the planted/silent cycle).
If you think your silent cycle is complete, you can proceed in a few different ways:
a) ammonia challenge
b) fish + bacterial starter
c) wait some more
a) ammonia challenge:
This is a surefire way to determine whether your tank is ready for fish. You will need an Ammonia and Nitrite test kit (nitrate test is optional, but recommended). An often used reliable product is the API Master Test Kit. You will also need pure ammonia (can be purchased from the hardware store - make sure it has NO added detergents/chemicals), there are also some fish brands like Dr. Tim's which sell ammonia in smaller quantities.
This ammonia challenge is designed to simulate the bioload of 1-3 fish (slightly more for a bigger tank). In a fishless cycle, ammonia concentrations up to 3ppm are used, but concentrations that high may risk causing harm to your plants.
steps:
1) add enough ammonia to measure 0.25-1ppm on your test kit. Have your filter on when adding the ammonia, and wait 30 minutes before testing to allow the ammonia to disperse in the water. Note: depending on what other plants you have, some plants may be sensitive to a sudden increase in ammonia. Alternatives for controlling that are adding the ammonia gradually over 24h, and/or adding a very small dose (you still need to be able to measure it on your test kit though).
2) 24h after you added ammonia, test your water for ammonia and nitrites. Both should read 0. If they do read 0, congratulations, you're done! Do a 75% water change and get your fish! Remember, only get a few fish at a time to avoid an ammonia spike.
If your reading 24h after ammonia is more than 0 for ammonia and nitrite, you can either get bacterial starter without fish, and keep testing your water every couple of days until you get a 0 reading on both ammonia and nitrites -> if that process seems to continue longer than 1 week, please post on the forum for advice! Or, you can do option c below.
Note: It is highly likely that a tank with a planted cycle will fail any attempt at a high (up to 3ppm) ammonia challenge. In this case, you will show a low reading of ammonia, and probably low or 0 nitrites. This is because in a planted cycle, there is initially no beneficial bacteria present to transform the ammonia into nitrates and nitrates, so any decrease in ammonia is simply dependent on how much your plants can take up in any certain amount of time. For further explanation, see "why is it called a silent cycle?" below, and the FAQ section.
b) fish + bacterial starter (optional):
If you feel reasonably comfortable that your plants have shown tremendous growth (and you have done your due diligence and posted a before and after picture on the forum and gotten the green light), go get yourself a very small number of fish! And a test kit for ammonia and nitrites, if you do not have one yet. It is best to only get a few (1-3) small fish at a time to avoid an ammonia spike. You can also optionally purchase a bacterial starter when you get your fish, since this will help the "silent" part of the silent cycle (described below).
After you get the fish, test the water daily for ammonia and nitrites, and if either is more than 0, do a 75% water change immediately. It is also advisable to use a water conditioner that detoxifies (but does not remove or neutralize) ammonia and nitrites. An example is Seachem Prime. Do not use products such as ammo-lock, nitri-zorb, zeolite, etc. The water should be tested daily for no less than 7 days, and you can stop testing once you have three days of 0 readings for both ammonia and nitrites. It is good practice to test the tank for ammonia and nitrites on a weekly-ish basis, just to determine if there are issues that are invisible to the naked eye. Depending on the fish you get, you should get into the habit of changing your water 25-50% every 1-2 weeks. Recommendations for this vary based on your stocking level, water parameters, fish choices, lifestyle, equipment, etc. Ask on the forum if you have questions!
Note: The number of fish to get depends primarily on the size of your tank, and what volume of the tank is made up of plant matter. In a tank that is 10 gallons (40L) or less, one fish or mystery snail should be the most that you start with. Smaller tanks are harder to control for water parameter swings in general, and starting slowly will mean a less stressful existence for both your fish as well as you. For larger tanks, up to three fish is an appropriate amount, and for very large tanks (>100g, >400L) 5-7 fish may be a good number of fish to start with. A planted/silent cycle very much falls into the camp of "slow and steady wins the race". If you add too many fish, you risk converting from a planted cycle into a fish-in cycle.
Note #2: certain fish species (tetras, corydoras, others) are to be kept in groups of 6 or more. It is appropriate to get only 3 of the fish to start with for a few weeks and then plan on filling out the herd once you are comfortable that your tank is able to keep up with the bioload of the 3 initial fish.
c) wait some more:
Does your after-photo only show moderate growth? Are you about to go on vacation? Can't be bothered with dealing with the fish tank right now? Who cares, wait some more! Do a water change after your first 2 weeks since your plants will need the trace minerals present in your water, and it might be worth considering adding some liquid fertilizer to keep them perky and full until you decide to add new inhabitants to your tank. You should get into the habit of changing ~50% of the water every two weeks while there are no inhabitants in the tank. If you have concerns, ask on the forum and people will be happy to help!
So why is it called a "Silent Cycle" anyway?
Unless you intend on your tank being lightly stocked and practically more plants than water forever (also called a Walstad-style tank), you will also need to establish a colony of beneficial bacteria into your tank. This article describes the nitrogen cycle and how the bacteria are established (written in the context of a fishelss cycle).
The point of a planted/silent cycle is that fast-growing plants remove ammonia, (and less preferentially) nitrites and nitrates from the water column up to a certain amount. The amount is determined by the ratio of plants to water in your tank (more plants -> more ammonia is consumed). If you only have one small fish in your tank and keep all of the fast-growing plants, your plants will take up all the waste toxins produced by your fish, and you will never see ammonia or nitrites or nitrates in your tank. However, as you add more fish, and as those fish grow, they will over time begin to produce more waste. This is a gradual process (this is why it is generally recommended to add only a few fish at a time), and the beauty of this process is that the plants help prevent any sudden spikes or changes in your tank parameters, allowing the beneficial bacteria that take up these excess waste products time to grow.
What happens in the background is that the ammonia that the fish produce circulates in the water before it "hits" something in the tank. Some of this ammonia ends up traveling through the filter, where it comes into contact with the filter media, and still other ammonia molecules may come into contact with the substrate before they come into contact with a plant. Over time, the filter media and the substrate begin to grow invisible beneficial bacteria which help break down ammonia, establishing the nitrogen cycle.
As is described in the article linked above, the beneficial bacteria convert ammonia into nitrites, and nitrites into nitrates, which are not toxic to your fish as long as they are under 20ppm. As these bacteria grow, the capacity of your tank to process fish waste increases. This is called a "mature" or "cycled" tank. In a planted/silent cycle, this process can be expected to last 3-6 months, but you may add new fish to the tank every few weeks as the tank does its thing. It is not easily possible to measure how this process is going, and it is dependent on many different variables. However, that is why if you don't like your fast-growing plants, you can begin to remove them gradually after 3-6 months (don't take them all out at once to give the bacteria time to adjust). Generally, in an established tank, the bacteria can compensate for changes in plant matter/fish stocking levels in 1-2 weeks.
If at any point, especially after adding new fish, you see an increase in ammonia or nitrites, it means that your beneficial bacteria/plants cannot keep up with the new influx of waste. You should do daily 75% water changes until both ammonia and nitrites read 0. Bacterial starter (such as tetra safe start plus or seachem stability) will also help in situations when an unexpected ammonia/nitrite spike occurs.
FAQ section
1) I tested my tank water and I measured ammonia and/or nitrites even though I have only plants in my tank!
There are a few possible reasons for this. Firstly, your tap water may contain chloramine (a commonly used water disinfectant in addition to chlorine). When you add water conditioner, the chloramine breaks down into ammonia and chlorine. If this is the case with your tap water, you will always have ammonia present in your tank from the start. For a planted cycle, this is a very good thing! It helps your plants to grow by providing them nutrients in the form of ammonia, and it also helps the background work of starting the beneficial bacterial colonies! In my own experience, partway through my planted cycle, I was not reading any ammonia, but was reading very high nitrites on my test kit. I did a water change to lower the nitrites, and also ended up getting a bacterial starter to help the cycle along (though I'm sure if I would have waited long enough, the tank would have nicely cycled itself!).
Another possible source of ammonia may be decaying plant bits. It is very common that plants for the aquarium trade are grown emersed, or in different conditions than your water. When the plants adjust, they discard old leaves and grow new ones in their place. These old leaves then decompose in your tank, and provide a source of ammonia. Again, if you do not have any inhabitants in your tank, this can be a good thing! It can help establish the beneficial bacteria, and will ready your aquarium for fish. However, if there is a lot of dead plant matter, you may be well served to vacuum or otherwise remove some of it, since you won't be able to add fish while you are still measuring ammonia/nitrites in your tank.
A third possibility for ammonia/nitrite readings could be your test kit. Is it expired? Have you tested it against untreated tap water? If your test kit requires you to compare colors, have you looked at the color in a well-lit location? You can also test filtered or spring water for comparison, since it should not have any ammonia (though interestingly enough some bottled water brands do contain nitrites or nitrates!). There are some anecdotal stories of some API ammonia test kits always reading a slight "green", so you may need to get comfortable with your test kit and verify that it does indeed read correctly (you can take a water sample to your fish store and they will usually test it for free as well).
2) What is a bacterial starter and why do I need one?
There are various different brands of bacterial starters on the market. Commonly used brands include Seachem Stability, Tetra Safe Start Plus, Aquaeon Pure Live Bacteria, API quick start, etc. It can be very tricky to navigate the market and evaluate which products are worth buying, and which ones do not measure up to the hype. I have personally had good results with Seachem Stability, and many members on this forum swear by Tetra Safe Start Plus. If you decide to buy a bacterial starter, it is important to read the description carefully, and to ensure that the product states that it will "establish your cycle" or "quick start the nitrogen cycle" or similar. Some products have descriptions on them that say "supports an aquarium cycle" or "helps break down fish waste", and in my experience these products do NOT contain the appropriate beneficial bacteria that you need to start a cycle in your tank. As just one example, API stress zyme does not help establish your cycle, so for the purposes of cycling your tank it is not the right product to use.
A bacterial starter, if it works, will help speed up the process of growing the beneficial bacteria in your tank. This will help support more fish faster in your tank. If your tap water has chloramine in it, you will be introducing ammonia directly into the tank, which may help cycle the tank without the need for bacterial starter. At the same time, because you are introducing ammonia into your tank, depending on how your plants do, you may need to help things along a little bit with a bacterial starter. Ultimately, it is personal preference, since until you add inhabitants, time is always on your side.
3) I did everything according to the directions and my plants grew, but when I added fish I have ammonia and/or nitrites in my tank. What happened?
This can definitely be a frustrating scenario, since seeing ammonia and/or nitrites after adding fish is definitely stressful! In all likelihood, you did nothing wrong. This happened to me too, even though I thought I did everything "right". There are a lot of variables that go into determining when a fish tank is "ready" for fish, and unfortunately, we don't have a good way of measuring everything that goes on in the tank. From a philosophical perspective, testing for ammonia and nitrites is somewhat "reactionary", since it shows that something is already off balance, and we don't have good tools at our disposal to predict when things may go off balance before it happens.
Fortunately, there are a few things you can do to remedy the situation. The least stressful option is probably to take the fish back, and ask if your LFS will either hold them for you or give you store credit until you are able to put fish into your tank. This may not always be an option, if you ordered your fish online, or if you buy your fish from a chain store and it's not a guarantee that the fish will be better off going back to the store.
Another option is to do frequent water changes of 50-75%, depending on what your test results are. Please ask on the forum, and we will be able to advise your individual situation! Using products such as Seachem Prime water conditioner will help detoxify ammonia and nitrites for 24 hours, and will help protect your fish between daily water changes.
In addition to water changes, you can head to the store and buy more fast-growing plants and/or bacterial starter. Both of these should help blunt the effects of ammonia/nitrites, and will help the health of your fish as well.
4) Wait two weeks?!?!? But I want fish now?! what the heck am I going to do with my life for two weeks?
Go drink yourself silly for all I care But in all seriousness, this is an excellent time to post on the forum and get others' feedback on your choices for fish selection! You can also continue to scape your tank - maybe you ordered a new decoration on amazon that you just had to have, no better time to wash it and put it in the tank than while everything is still establishing itself!
5) I have algae.
This can happen with a planted cycle. In general, the more plants you have the less likely you are to get algae, but if algae does show up, you can begin by shortening the duration that the lights are on in the tank. If you are not at home or have a tendency to forget, use a timer to control the lights. Other causes of algae can be a nutrient imbalance, for example. Look on the Algae management section of the forum for some ideas, and post your question if reducing the light period doesn't work!
6) I got my first fish, and two weeks later my water is still testing at 0 ammonia and 0 nitrites. What next?
Yay! That is great news! The next step is to slowly add more fish, preferably 3 at a time. Keep up the good work!
You have a few options:
1) Fishless cycle: Set up your substrate and filter (decorations and plants are optional), buy pure ammonia, add enough to your tank to read 3ppm, wait. Full instructions here: https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/
2) Planted/Silent cycle: the focus of this article
3) Fish-in cycle: set up your tank, add 1-3 fish, test ammonia and nitrites daily, do 75%+ water changes daily until ammonia and nitrites go to zero, and pray that your fish don't die. Additional instructions here: https://www.fishforums.net/threads/rescuing-a-fish-in-cycle-gone-wild-part-i.433769/
Which option is best for you? Depends on your personality and experience level, as well as how much work and stress you want. (hint:: option #3 is the most stressful and labor intensive). If you like chemistry and measuring things, and don't want to mess with plants, then option 1 is probably a great fit for you. If you want to get your hands wet right away, and don't mind some stuff floating around your tank for a couple of months until things stabilize, then option 2 may be worth considering! For the sake of the fish, don't do option 3 as your first choice. Options 1 and 2 are more ethical approaches to cycling a tank.
Please note, that with both a planted/silent cycle and a fish-in cycle, inhabitants must be added gradually (no more than 1-3 at a time) to the tank. If you want to take an approach where you get most of your fish in one fell swoop (if you are ordering stock online for example) then a fishless cycle is recommended.
The rest of this article focuses on how to do a Planted/Silent cycle. Credit for all of this knowledge goes to the wonderful people on this forum, without which I could not have compiled any of this information! A special thank you especially to @Essjay, who proofread this upteen times
To set up a planted/silent cycle, do the following:
1) leak test your aquarium
2) wash and place the substrate, filter, heater, thermometer, light(s) and any other hardware you wish to add. Fill up your tank, and add water conditioner/dechlorinator if your water requires it. I suppose this is technically optional with no inhabitants, but you're going to need it anyway in the future so might as well get in the habit.
3) acquire many fast-growing plants, in addition to any other plants you may wish to include in your aquascape at this point. The fast-growing plants are ideally ones that feed directly from the water column. You are not obligated to keep the fast-growing plants forever, but for the purposes of getting your tank cycled and your fish added, be prepared to have the plants in there for 3-6 months. You should aim to have at LEAST 30% of your water VOLUME filled with plant matter.
Examples of plants that are good to use for a planted/silent cycle are:
Hornwort
Elodea / anacharis / water weed / pond weed: actually a family of plants, but most of them work relatively well. One common example: look for "egeria densa" (also called elodea densa)
Frogbit
Duckweed (note, this may be difficult to get rid of due to its small size, but will not do well in a high current.)
Water sprite / water wisteria (similar plants, but water sprite may be slightly better suited due to its preference for leaf feeding, but both are fast-growing plants)
Because many of these plants are fast growing, they are also considered invasive and may be illegal in specific areas. Please check with your local authority before buying these plants online to determine whether they are considered invasive. To dispose of the plants listed above, please boil or fully dry them before placing them in the TRASH or deep into a compost heap (not down the drain or near any other water source). Many of these plant species will propagate from a tiny fraction of a leaf, which is why they pose a risk of being invasive.
4) Take a picture of your tank to document how big the plants are. Set your lights on a timer so that the plants get 6-10h of light (depending on then intensity of your particular light bulb. If you start to get algae, give less light).
5) (optional) add root tabs or liquid fertilizers (as appropriate for the plants you have - the plants listed above do not need root tabs) to your tank. This will help speed up the plant growth in the absence of fish waste.
6) go do something else with your life for a while, and two weeks later, compare your photo to the present situation. If there is significant growth, your silent cycle could be complete!
7) Once your cycle is complete, fish should be added gradually and slowly. Unless your goal is a Walstad-style tank, your inhabitants may ultimately produce more ammonia than what your plants will ever be able to handle (this largely depends on the plant species in your tank), which is why you need to allow time for the beneficial bacteria to establish themselves in your tank in the background (the "silent" part of the planted/silent cycle).
If you think your silent cycle is complete, you can proceed in a few different ways:
a) ammonia challenge
b) fish + bacterial starter
c) wait some more
a) ammonia challenge:
This is a surefire way to determine whether your tank is ready for fish. You will need an Ammonia and Nitrite test kit (nitrate test is optional, but recommended). An often used reliable product is the API Master Test Kit. You will also need pure ammonia (can be purchased from the hardware store - make sure it has NO added detergents/chemicals), there are also some fish brands like Dr. Tim's which sell ammonia in smaller quantities.
This ammonia challenge is designed to simulate the bioload of 1-3 fish (slightly more for a bigger tank). In a fishless cycle, ammonia concentrations up to 3ppm are used, but concentrations that high may risk causing harm to your plants.
steps:
1) add enough ammonia to measure 0.25-1ppm on your test kit. Have your filter on when adding the ammonia, and wait 30 minutes before testing to allow the ammonia to disperse in the water. Note: depending on what other plants you have, some plants may be sensitive to a sudden increase in ammonia. Alternatives for controlling that are adding the ammonia gradually over 24h, and/or adding a very small dose (you still need to be able to measure it on your test kit though).
2) 24h after you added ammonia, test your water for ammonia and nitrites. Both should read 0. If they do read 0, congratulations, you're done! Do a 75% water change and get your fish! Remember, only get a few fish at a time to avoid an ammonia spike.
If your reading 24h after ammonia is more than 0 for ammonia and nitrite, you can either get bacterial starter without fish, and keep testing your water every couple of days until you get a 0 reading on both ammonia and nitrites -> if that process seems to continue longer than 1 week, please post on the forum for advice! Or, you can do option c below.
Note: It is highly likely that a tank with a planted cycle will fail any attempt at a high (up to 3ppm) ammonia challenge. In this case, you will show a low reading of ammonia, and probably low or 0 nitrites. This is because in a planted cycle, there is initially no beneficial bacteria present to transform the ammonia into nitrates and nitrates, so any decrease in ammonia is simply dependent on how much your plants can take up in any certain amount of time. For further explanation, see "why is it called a silent cycle?" below, and the FAQ section.
b) fish + bacterial starter (optional):
If you feel reasonably comfortable that your plants have shown tremendous growth (and you have done your due diligence and posted a before and after picture on the forum and gotten the green light), go get yourself a very small number of fish! And a test kit for ammonia and nitrites, if you do not have one yet. It is best to only get a few (1-3) small fish at a time to avoid an ammonia spike. You can also optionally purchase a bacterial starter when you get your fish, since this will help the "silent" part of the silent cycle (described below).
After you get the fish, test the water daily for ammonia and nitrites, and if either is more than 0, do a 75% water change immediately. It is also advisable to use a water conditioner that detoxifies (but does not remove or neutralize) ammonia and nitrites. An example is Seachem Prime. Do not use products such as ammo-lock, nitri-zorb, zeolite, etc. The water should be tested daily for no less than 7 days, and you can stop testing once you have three days of 0 readings for both ammonia and nitrites. It is good practice to test the tank for ammonia and nitrites on a weekly-ish basis, just to determine if there are issues that are invisible to the naked eye. Depending on the fish you get, you should get into the habit of changing your water 25-50% every 1-2 weeks. Recommendations for this vary based on your stocking level, water parameters, fish choices, lifestyle, equipment, etc. Ask on the forum if you have questions!
Note: The number of fish to get depends primarily on the size of your tank, and what volume of the tank is made up of plant matter. In a tank that is 10 gallons (40L) or less, one fish or mystery snail should be the most that you start with. Smaller tanks are harder to control for water parameter swings in general, and starting slowly will mean a less stressful existence for both your fish as well as you. For larger tanks, up to three fish is an appropriate amount, and for very large tanks (>100g, >400L) 5-7 fish may be a good number of fish to start with. A planted/silent cycle very much falls into the camp of "slow and steady wins the race". If you add too many fish, you risk converting from a planted cycle into a fish-in cycle.
Note #2: certain fish species (tetras, corydoras, others) are to be kept in groups of 6 or more. It is appropriate to get only 3 of the fish to start with for a few weeks and then plan on filling out the herd once you are comfortable that your tank is able to keep up with the bioload of the 3 initial fish.
c) wait some more:
Does your after-photo only show moderate growth? Are you about to go on vacation? Can't be bothered with dealing with the fish tank right now? Who cares, wait some more! Do a water change after your first 2 weeks since your plants will need the trace minerals present in your water, and it might be worth considering adding some liquid fertilizer to keep them perky and full until you decide to add new inhabitants to your tank. You should get into the habit of changing ~50% of the water every two weeks while there are no inhabitants in the tank. If you have concerns, ask on the forum and people will be happy to help!
So why is it called a "Silent Cycle" anyway?
Unless you intend on your tank being lightly stocked and practically more plants than water forever (also called a Walstad-style tank), you will also need to establish a colony of beneficial bacteria into your tank. This article describes the nitrogen cycle and how the bacteria are established (written in the context of a fishelss cycle).
The point of a planted/silent cycle is that fast-growing plants remove ammonia, (and less preferentially) nitrites and nitrates from the water column up to a certain amount. The amount is determined by the ratio of plants to water in your tank (more plants -> more ammonia is consumed). If you only have one small fish in your tank and keep all of the fast-growing plants, your plants will take up all the waste toxins produced by your fish, and you will never see ammonia or nitrites or nitrates in your tank. However, as you add more fish, and as those fish grow, they will over time begin to produce more waste. This is a gradual process (this is why it is generally recommended to add only a few fish at a time), and the beauty of this process is that the plants help prevent any sudden spikes or changes in your tank parameters, allowing the beneficial bacteria that take up these excess waste products time to grow.
What happens in the background is that the ammonia that the fish produce circulates in the water before it "hits" something in the tank. Some of this ammonia ends up traveling through the filter, where it comes into contact with the filter media, and still other ammonia molecules may come into contact with the substrate before they come into contact with a plant. Over time, the filter media and the substrate begin to grow invisible beneficial bacteria which help break down ammonia, establishing the nitrogen cycle.
As is described in the article linked above, the beneficial bacteria convert ammonia into nitrites, and nitrites into nitrates, which are not toxic to your fish as long as they are under 20ppm. As these bacteria grow, the capacity of your tank to process fish waste increases. This is called a "mature" or "cycled" tank. In a planted/silent cycle, this process can be expected to last 3-6 months, but you may add new fish to the tank every few weeks as the tank does its thing. It is not easily possible to measure how this process is going, and it is dependent on many different variables. However, that is why if you don't like your fast-growing plants, you can begin to remove them gradually after 3-6 months (don't take them all out at once to give the bacteria time to adjust). Generally, in an established tank, the bacteria can compensate for changes in plant matter/fish stocking levels in 1-2 weeks.
If at any point, especially after adding new fish, you see an increase in ammonia or nitrites, it means that your beneficial bacteria/plants cannot keep up with the new influx of waste. You should do daily 75% water changes until both ammonia and nitrites read 0. Bacterial starter (such as tetra safe start plus or seachem stability) will also help in situations when an unexpected ammonia/nitrite spike occurs.
FAQ section
1) I tested my tank water and I measured ammonia and/or nitrites even though I have only plants in my tank!
There are a few possible reasons for this. Firstly, your tap water may contain chloramine (a commonly used water disinfectant in addition to chlorine). When you add water conditioner, the chloramine breaks down into ammonia and chlorine. If this is the case with your tap water, you will always have ammonia present in your tank from the start. For a planted cycle, this is a very good thing! It helps your plants to grow by providing them nutrients in the form of ammonia, and it also helps the background work of starting the beneficial bacterial colonies! In my own experience, partway through my planted cycle, I was not reading any ammonia, but was reading very high nitrites on my test kit. I did a water change to lower the nitrites, and also ended up getting a bacterial starter to help the cycle along (though I'm sure if I would have waited long enough, the tank would have nicely cycled itself!).
Another possible source of ammonia may be decaying plant bits. It is very common that plants for the aquarium trade are grown emersed, or in different conditions than your water. When the plants adjust, they discard old leaves and grow new ones in their place. These old leaves then decompose in your tank, and provide a source of ammonia. Again, if you do not have any inhabitants in your tank, this can be a good thing! It can help establish the beneficial bacteria, and will ready your aquarium for fish. However, if there is a lot of dead plant matter, you may be well served to vacuum or otherwise remove some of it, since you won't be able to add fish while you are still measuring ammonia/nitrites in your tank.
A third possibility for ammonia/nitrite readings could be your test kit. Is it expired? Have you tested it against untreated tap water? If your test kit requires you to compare colors, have you looked at the color in a well-lit location? You can also test filtered or spring water for comparison, since it should not have any ammonia (though interestingly enough some bottled water brands do contain nitrites or nitrates!). There are some anecdotal stories of some API ammonia test kits always reading a slight "green", so you may need to get comfortable with your test kit and verify that it does indeed read correctly (you can take a water sample to your fish store and they will usually test it for free as well).
2) What is a bacterial starter and why do I need one?
There are various different brands of bacterial starters on the market. Commonly used brands include Seachem Stability, Tetra Safe Start Plus, Aquaeon Pure Live Bacteria, API quick start, etc. It can be very tricky to navigate the market and evaluate which products are worth buying, and which ones do not measure up to the hype. I have personally had good results with Seachem Stability, and many members on this forum swear by Tetra Safe Start Plus. If you decide to buy a bacterial starter, it is important to read the description carefully, and to ensure that the product states that it will "establish your cycle" or "quick start the nitrogen cycle" or similar. Some products have descriptions on them that say "supports an aquarium cycle" or "helps break down fish waste", and in my experience these products do NOT contain the appropriate beneficial bacteria that you need to start a cycle in your tank. As just one example, API stress zyme does not help establish your cycle, so for the purposes of cycling your tank it is not the right product to use.
A bacterial starter, if it works, will help speed up the process of growing the beneficial bacteria in your tank. This will help support more fish faster in your tank. If your tap water has chloramine in it, you will be introducing ammonia directly into the tank, which may help cycle the tank without the need for bacterial starter. At the same time, because you are introducing ammonia into your tank, depending on how your plants do, you may need to help things along a little bit with a bacterial starter. Ultimately, it is personal preference, since until you add inhabitants, time is always on your side.
3) I did everything according to the directions and my plants grew, but when I added fish I have ammonia and/or nitrites in my tank. What happened?
This can definitely be a frustrating scenario, since seeing ammonia and/or nitrites after adding fish is definitely stressful! In all likelihood, you did nothing wrong. This happened to me too, even though I thought I did everything "right". There are a lot of variables that go into determining when a fish tank is "ready" for fish, and unfortunately, we don't have a good way of measuring everything that goes on in the tank. From a philosophical perspective, testing for ammonia and nitrites is somewhat "reactionary", since it shows that something is already off balance, and we don't have good tools at our disposal to predict when things may go off balance before it happens.
Fortunately, there are a few things you can do to remedy the situation. The least stressful option is probably to take the fish back, and ask if your LFS will either hold them for you or give you store credit until you are able to put fish into your tank. This may not always be an option, if you ordered your fish online, or if you buy your fish from a chain store and it's not a guarantee that the fish will be better off going back to the store.
Another option is to do frequent water changes of 50-75%, depending on what your test results are. Please ask on the forum, and we will be able to advise your individual situation! Using products such as Seachem Prime water conditioner will help detoxify ammonia and nitrites for 24 hours, and will help protect your fish between daily water changes.
In addition to water changes, you can head to the store and buy more fast-growing plants and/or bacterial starter. Both of these should help blunt the effects of ammonia/nitrites, and will help the health of your fish as well.
4) Wait two weeks?!?!? But I want fish now?! what the heck am I going to do with my life for two weeks?
Go drink yourself silly for all I care
But in all seriousness, this is an excellent time to post on the forum and get others' feedback on your choices for fish selection! You can also continue to scape your tank - maybe you ordered a new decoration on amazon that you just had to have, no better time to wash it and put it in the tank than while everything is still establishing itself!5) I have algae.
This can happen with a planted cycle. In general, the more plants you have the less likely you are to get algae, but if algae does show up, you can begin by shortening the duration that the lights are on in the tank. If you are not at home or have a tendency to forget, use a timer to control the lights. Other causes of algae can be a nutrient imbalance, for example. Look on the Algae management section of the forum for some ideas, and post your question if reducing the light period doesn't work!
6) I got my first fish, and two weeks later my water is still testing at 0 ammonia and 0 nitrites. What next?
Yay! That is great news! The next step is to slowly add more fish, preferably 3 at a time. Keep up the good work!
