Quarantine Tank - Corys

[bettacarl]

Morning! I am currently cycling my quarantine tank and wanted to get corys once it's done. I have a 5 gallon quarantine tank and eventually they will be going into a 29 gallon tank. I know corys like schools of at least 6, so if I got 6, would they be OK in the 5 gallon for a few weeks? Or do I need to split the grouping up some how?

 

[Byron]

Morning! I am currently cycling my quarantine tank and wanted to get corys once it's done. I have a 5 gallon quarantine tank and eventually they will be going into a 29 gallon tank. I know corys like schools of at least 6, so if I got 6, would they be OK in the 5 gallon for a few weeks? Or do I need to split the grouping up some how?

They will be fine, but you need more of them. As the display tank is 29g, I would suggest a group of cories somewhere between 9 and 12. It can be one species, or mixed, but the numbers really do matter. And if you acquire all of them together, they will be fine in the QT for a few weeks. In most cases, cories are offered in stores when very young, and thus small. Make sure you have some soft sand on the tank floor. And floating plants will shade the tank and allow them to settle in much faster. This is the benefit of a larger group acquired together--much less chance of stress causing ich.

 

[bettacarl]

Shoot, I have gravel in the tank right now (not the quarantine tank, but the 29 gallon tank). After reading your reply I did some research and some people have said you can also use 'soft' gravel. What is soft gravel? Does anyone have a link or picture of what the 'soft' gravel is?

Otherwise my only concern with the sand is that I have read that it can create pockets of dangerous bacteria and that the sand can potentially get sucked into the filter and ruin it.

 

[squidneh]

Shoot, I have gravel in the tank right now (not the quarantine tank, but the 29 gallon tank). After reading your reply I did some research and some people have said you can also use 'soft' gravel. What is soft gravel? Does anyone have a link or picture of what the 'soft' gravel is?

Otherwise my only concern with the sand is that I have read that it can create pockets of dangerous bacteria and that the sand can potentially get sucked into the filter and ruin it.

Sand is a very common substrate because plants do well in it and it is safe for most any kind of fish (whereas as you've learned, gravel isn't safe for all fish). If I were you I would swap the tank to sand substrate now rather than later as it's much easier to do before the tank is established. Or if your 29 gallon is already running, then perhaps leave the gravel but opt for Otocinclus instead of Cory cats... or just swap it anyways!

If you're worried about anaerobic pockets in the sand you can easily fix that with Malaysian Trumpet Snails. They burrow into the sand and prevent the pockets from forming. As long as you don't overfeed their numbers will remain under control.

I've never heard of sand ruining a filter although I guess theoretically it COULD happen. Sand isn't in the water column typically - maybe if you REALLY stir it up on purpose, but usually if you're doing that deep of a clean the filter would be off, anyway. But typically, once sand is cleaned (rinsed in a bucket with water prior to adding to tank) and put into the tank, it will sink straight back to the bottom - not get sucked into the filter. I vacuum the top of my sand once a week and it goes up into the siphon and then falls right back out onto the bottom.

 

[Byron]

Shoot, I have gravel in the tank right now (not the quarantine tank, but the 29 gallon tank). After reading your reply I did some research and some people have said you can also use 'soft' gravel. What is soft gravel? Does anyone have a link or picture of what the 'soft' gravel is?

Otherwise my only concern with the sand is that I have read that it can create pockets of dangerous bacteria and that the sand can potentially get sucked into the filter and ruin it.

Taking the last issue first, this is somewhat misleading. Any substrate can become dangerous, if it is too deep, the wrong material, not properly cared for, etc, etc. Sand is without question the best substrate material in an aquarium as far as plants and fish are concerned; the only exceptions are those larger (usually) fish that occur in gravel habitats. A sand depth overall (when first added to the empty tank and spread out evenly) of 1.5 to 2 inches (4-5 cm) is usually adequate. Areas under chunks of wood and rock will become anaerobic, or may, but this is natural and part of a healthy biological system, so don't disturb such areas. As for the filter issue, don't have the filter intake close to the substrate, have it about 3-4 inches above. I have never seen sand pulled into any of my internal or canister filters in the 9 years I have had sand.

Corydoras must have sand. They are filter feeders, and they take in a mouthful of sand, filter out food, and expel most of the sand via the gills; some sand is ingested and comes out the other end. Non-rough sand is essential to avoid damaging the delicate gills and digestive tract. And this process is impossible for the fish with gravel.

Sand must be non-angular and not rough. And it must be inert, meaning it is not composed of calcareous rock material. Aquarium river sands purchased in a fish store or online aree OK, or you can use a good quality play sand. Do not use any other type of industrial sand. Quikrete Play Sand (available in NA) is good, and in the UK the Argos pPlay Sand is endorsed by UK members.

 

[bettacarl]

Taking the last issue first, this is somewhat misleading. Any substrate can become dangerous, if it is too deep, the wrong material, not properly cared for, etc, etc. Sand is without question the best substrate material in an aquarium as far as plants and fish are concerned; the only exceptions are those larger (usually) fish that occur in gravel habitats. A sand depth overall (when first added to the empty tank and spread out evenly) of 1.5 to 2 inches (4-5 cm) is usually adequate. Areas under chunks of wood and rock will become anaerobic, or may, but this is natural and part of a healthy biological system, so don't disturb such areas. As for the filter issue, don't have the filter intake close to the substrate, have it about 3-4 inches above. I have never seen sand pulled into any of my internal or canister filters in the 9 years I have had sand.

Corydoras must have sand. They are filter feeders, and they take in a mouthful of sand, filter out food, and expel most of the sand via the gills; some sand is ingested and comes out the other end. Non-rough sand is essential to avoid damaging the delicate gills and digestive tract. And this process is impossible for the fish with gravel.

Sand must be non-angular and not rough. And it must be inert, meaning it is not composed of calcareous rock material. Aquarium river sands purchased in a fish store or online aree OK, or you can use a good quality play sand. Do not use any other type of industrial sand. Quikrete Play Sand (available in NA) is good, and in the UK the Argos pPlay Sand is endorsed by UK members.

Great information, thank you. Do you still clean the sand once a week with a siphon hose? Are there any other things that need to be done to keep the sand clean and the tank healthy?

 

[bettacarl]

Sand is a very common substrate because plants do well in it and it is safe for most any kind of fish (whereas as you've learned, gravel isn't safe for all fish). If I were you I would swap the tank to sand substrate now rather than later as it's much easier to do before the tank is established. Or if your 29 gallon is already running, then perhaps leave the gravel but opt for Otocinclus instead of Cory cats... or just swap it anyways!

If you're worried about anaerobic pockets in the sand you can easily fix that with Malaysian Trumpet Snails. They burrow into the sand and prevent the pockets from forming. As long as you don't overfeed their numbers will remain under control.

I've never heard of sand ruining a filter although I guess theoretically it COULD happen. Sand isn't in the water column typically - maybe if you REALLY stir it up on purpose, but usually if you're doing that deep of a clean the filter would be off, anyway. But typically, once sand is cleaned (rinsed in a bucket with water prior to adding to tank) and put into the tank, it will sink straight back to the bottom - not get sucked into the filter. I vacuum the top of my sand once a week and it goes up into the siphon and then falls right back out onto the bottom.

Thanks for the information! Yea, I just have the mollies in the 29 gallon right now so I think I'll switch it to sand before it becomes more difficult. I wish I had known that before putting the things in there, but at least I learned what is best for the fish. Do you happen to know, since I already have that tank established, if removing the gravel will remove too much of the good bacteria?

 

[Byron]

Great information, thank you. Do you still clean the sand once a week with a siphon hose? Are there any other things that need to be done to keep the sand clean and the tank healthy?

In some tanks I never touch the sand substrate (my cory tank for one, they filter feed so thoroughly I never need to), while in another I might do a quick sweep over the top in open areas, depending. Live plants rooted in the sand help, as do snails especially Malaysian Livebearing Snails that borrow through the substrate.

 

[Byron]

The substrate is the most important bacteria bed in the aquarium, far more important than the filter. Many different species of bacteria, with different roles, live in the substrate. Removing the gravel substrate will obviously remove all of these as bacteria are sticky and live on surfaces, but they will rapidly reappear with sand. Keep the filter wet to preserve the nitrifying bacteria and there should be no problem changing substrates. Live plants if present are also beneficial.

 

[Essjay]

I just have the mollies in the 29 gallon right now

I have just noticed you have mollies. Are you aware that mollies are hard water fish while cories are soft water fish? They are not compatible on hardness grounds. Depending on your tap water hardness, one or other will not be happy.
Do you have hard or soft water? You water provider's website should tell you how hard your water is; you need a number and the unit of measurement.

 

[bettacarl]

I have just noticed you have mollies. Are you aware that mollies are hard water fish while cories are soft water fish? They are not compatible on hardness grounds. Depending on your tap water hardness, one or other will not be happy.
Do you have hard or soft water? You water provider's website should tell you how hard your water is; you need a number and the unit of measurement.

That surprises me that they aren't compatible since I've seen so many different sites and references saying they are. That is unfortunate! As for the water hardness, I hadn't looked at that before. I just looked it up the water hardness, and in my city, it is only 101ppm or 6 gpg. How can I make the water harder? And how do I measure my water once I raise the hardness?

 

[bettacarl]

The substrate is the most important bacteria bed in the aquarium, far more important than the filter. Many different species of bacteria, with different roles, live in the substrate. Removing the gravel substrate will obviously remove all of these as bacteria are sticky and live on surfaces, but they will rapidly reappear with sand. Keep the filter wet to preserve the nitrifying bacteria and there should be no problem changing substrates. Live plants if present are also beneficial.

Alright thanks for the information! I plan on changing out the substrate today even if I don't get corydoras since it sounds like sand is a better choice. I'll just keep an eye on the parameters and hopefully the bacteria will come back quickly.

 

[Byron]

That surprises me that they aren't compatible since I've seen so many different sites and references saying they are. That is unfortunate! As for the water hardness, I hadn't looked at that before. I just looked it up the water hardness, and in my city, it is only 101ppm or 6 gpg. How can I make the water harder? And how do I measure my water once I raise the hardness?

As for measuring, there are test kits for GH and KH, like the API. The GH will not change much if at all in the aquarium from the source water level, unless you (the aquarist) somehow targets it. Which brings me to your question how to increase GH.

This is a two-edged sword. Mollies absolutely must have harder water than what you have, considerably so, or they will not last long (a few months at best). The GH is the dissolved calcium and magnesium in the water, and livebearers have evolved to live in water relatively high in calcium especially, and their physiology uses the dissolved calcium taken from the water entering the fish though every cell. This is crucial to their functioning and health.

However, soft water fish are somewhat the opposite; they have evolved to not need/use minerals from the water, and when kept in hard water the assimilation of the calcium by the fish's kidneys leads to calcium blockage and death. The point being, that soft water fish like cories will be healthier in softer water, such as what you have (and even softer, but the 6 dGH you have is not a problem as is). If you increase the GH by at least double (actually, more than this for mollies) you will be impacting the cories. A better option would be to decide which fish you want, softish water or the mollies. Given you have soft water it will make life much easier for you and your fish if you stay with fish species that prefer softer water. Re-home the mollies, or let them die off in time. Or acquire a second tank large enough for the mollies and provide harder water.

You can increase water hardness by using a calcareous substrate, or by the use of mineral salts added to the water. Mineral salts are not common table salt, but the salts of calcium and magnesium primarily. This means mixing replacement water outside the aquarium for all water changes so the tank water remains consistent at whatever GH you work toward. I have done this some years ago, and it is extra work and expense; selecting fish suited to your tap water is much easier on you and fish.

 

[Essjay]

That surprises me that they aren't compatible since I've seen so many different sites and references saying they are.

Most fish stores and a lot of websites have no idea that hardness is important for fish so they only think about behaviour, unfortunately.

 

[bettacarl]

As for measuring, there are test kits for GH and KH, like the API. The GH will not change much if at all in the aquarium from the source water level, unless you (the aquarist) somehow targets it. Which brings me to your question how to increase GH.

This is a two-edged sword. Mollies absolutely must have harder water than what you have, considerably so, or they will not last long (a few months at best). The GH is the dissolved calcium and magnesium in the water, and livebearers have evolved to live in water relatively high in calcium especially, and their physiology uses the dissolved calcium taken from the water entering the fish though every cell. This is crucial to their functioning and health.

However, soft water fish are somewhat the opposite; they have evolved top not need/use minerals from the water, and when kept in hard water the assimilation of the calcium by the fish's kidneys leads to calcium blockage and death. The point being, that soft water fish like cories will be healthier in softer water, such as what you have (and even softer, but the 6 dGH you have is not a problem as is). If you increase the GH by at least double (actually, more than this for mollies) you will be impacting the cories. A better option would be to decide which fish you want, softish water or the mollies. Given you have soft water it will make life much easier for you and your fish if you stay with fish species that prefer softer water. Re-home the mollies, or let them die off in time. Or acquire a second tank large enough for the mollies and provide harder water.

You can increase water hardness by using a calcareous substrate, or by the use of mineral salts added to the water. Mineral salts are not common table salt, but the salts of calcium and magnesium primarily. This means mixing replacement water outside the aquarium for all water changes so the tank water remains consistent at whatever GH you work toward. I have done this some years ago, and it is extra work and expense; selecting fish suited to your tap water is much easier on you and fish.

Thank you for all the information you've given. I wish the fish stores were more informed so I could have figured this out before purchasing the mollies. I will probably rehome them if I can. Do you happen to know (I am almost 100% sure the 15 days have come and gone for the petsmart return) if petsmart would take these fish back even if I don't get money back for them?