3 week old tank killing emerald corys

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Michael Ohair

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Hi all, we got a 10 gallon tank with 3 Male guppies and 1 emerald cory. The cory lives 1 week and dies. We just lost our 3rd and won't be getting any more. The guppies are thriving.

It's been 3 weeks. I used water conditioner and good bacteria starter. I check the water stats daily. 0 nitrate/nitrite, between 7-7.5 ph, 80 kh and very high gh. Our water is very hard out here. Temperature is 78 we have a heater. And I've done two 10% water changes with a gravel vacuum.

Any idea why they are dying.
 
You don't give a reading for ammonia. This is the first thing to increase, well before nitrite shows up. If you don't have a tester for ammonia, you need to get one asap as there could be ammonia in the water.
Cories are shoaling fish and need to be in a group of at least 6. But you do not have room in a 10 gallon tank for 6 emerald cories.
Cories are soft water fish, so your hard water is not suitable for them - though it is good for guppies.
All these will stress the cory and stressed fish get sick more easily.



If this was my tank, I would get an ammonia tester and test the tank water for both ammonia and nitrite every day. If ammonia is always zero, good. If not, I would do a water change every time the tester showed a reading above zero - and the same if/when nitrite starts to appear.
Then when ammonia and nitrite stay at zero by themselves, get a few more male guppies and no other fish.
 
Hi and welcome to the forum :)

Do not get any more fish until this matter is resolved.

As Essjay has pointed out, the most likely reason for the fish dying is ammonia.
Anything that breaks down in the water, be it fish food, fish waste, dead plant, dead fish, etc, produce ammonia. In a healthy tank with an established filter, the ammonia is eaten by beneficial bacteria and converted into nitrite. You get more good bacteria that eat nitrite and convert it into nitrate. You get rid of nitrates by doing water changes.

In a new tank the bacteria is not normally present and you get a build up of ammonia that harms and can kill the fish. A few weeks after the tank has been set up, you get the first colonies of good bacteria that eat the ammonia. A couple of weeks after that you start to get the other good bacteria that eat the nitrite. It normally takes about 4-6 weeks for an aquarium to develop the colonies of good bacteria that keep the ammonia and nitrite levels at 0.

When the ammonia and nitrite levels have gone up and come back down to 0, and the nitrate levels start to go up, the tank will be considered cycled (developed the necessary good filter bacteria) and you can feed the fish once or twice a day and do a 75% water change once a week. Until then you keep feeding down and water changes up. By reducing the food going into the tank, you help to keep the ammonia levels lower. By doing big water changes, you help to dilute any ammonia in the water.

In a newly set up aquarium, you should feed the fish to 2-3 times per week. Don't worry, the fish won't starve. You should also do a 75% water change and gravel clean the substrate 4-8 hours after feeding. And you should monitor the ammonia and nitrite levels and do a 75% water change any day you have an ammonia or nitrite reading above 0, or a nitrate reading above 20ppm.

*NB* Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

The big water changes will not harm the filter bacteria or fish as long as any new water is free of chlorine/ chloramine before it is added to the tank.

-------------------------
During the first month of a tank's cycle, you monitor the ammonia and nitrite levels. You normally get ammonia readings for the first few weeks. The ammonia goes up and as the beneficial filter bacteria build up in numbers they gradually convert the ammonia into nitrite. After a few weeks the ammonia level will suddenly drop to 0 and the nitrite will start to go up. A couple of weeks later the nitrite levels drop to 0 and the nitrates start to go up. You get rid of nitrates by doing water changes.

During the cycling period you do not test for nitrates until the ammonia and nitrite have gone up and come back down to 0. Nitrate test kits will read nitrite as nitrate and give you a false reading. So you monitor ammonia during the first few weeks and then start monitoring nitrite as well. Once they have both gone up and come down to 0, you start monitoring nitrate.

-------------------------
Do not clean the new filter for the first 6-8 weeks. This allows the filter bacteria a chance to settle in properly and stick to the filter media. Two weeks after the filters have finished cycling, you can start to clean the filter.

Established filters should be cleaned at least once a month and every 2 weeks is better.

To clean a power filter or internal sponge/ box filter. You get a bucket of water from the aquarium and squeeze the filter materials out in the bucket of tank water. When they are clean you put them in the aquarium. Wash/ rinse the filter case and impellor assembly (for a power filter) under tap water. Remove any excess tap water by tipping the filter case upside down, then put the filter materials back into the filter and set it back up and get it going.

If you have an undergravel filter, that will be cleaned when you do water changes and gravel clean the substrate. You can buy a basic model gravel cleaner from any pet shop and they are worth getting. You only need a basic model gravel cleaner like the one in the following link. Do not buy the expensive fancy types because they are no better than a base model gravel cleaner.
https://www.about-goldfish.com/aquarium-cleaning.html

----------------
If you have a filter that containers pads/ cartridges that need replacing on a regular basis, do not replace them. Go to the pet shop and buy some sponge for a different brand of filter (I use AquaClear sponges but there are other brands), and use a pair of scissors to cut the sponge to fit in your filter. Keep the sponge and filter pads together for 2 months, then remove the pads and throw them away. Replace the pads with more sponge.

Sponges get squeezed out in a bucket of tank water and will last 10+ years.

You can also get round/ cylindrical sponges for some brands of internal power filter. These round sponges have a hole through the centre and they fit over the intake strainer of most external power filters. They add extra filtration and prevent small fish and bits of plant form being sucked into the filter.
 
You don't give a reading for ammonia. This is the first thing to increase, well before nitrite shows up. If you don't have a tester for ammonia, you need to get one asap as there could be ammonia in the water.
Cories are shoaling fish and need to be in a group of at least 6. But you do not have room in a 10 gallon tank for 6 emerald cories.
Cories are soft water fish, so your hard water is not suitable for them - though it is good for guppies.
All these will stress the cory and stressed fish get sick more easily.



If this was my tank, I would get an ammonia tester and test the tank water for both ammonia and nitrite every day. If ammonia is always zero, good. If not, I would do a water change every time the tester showed a reading above zero - and the same if/when nitrite starts to appear.
Then when ammonia and nitrite stay at zero by themselves, get a few more male guppies and no other fish.


Thank you. I will do all that.
 
Hi and welcome to the forum :)

Do not get any more fish until this matter is resolved.

As Essjay has pointed out, the most likely reason for the fish dying is ammonia.
Anything that breaks down in the water, be it fish food, fish waste, dead plant, dead fish, etc, produce ammonia. In a healthy tank with an established filter, the ammonia is eaten by beneficial bacteria and converted into nitrite. You get more good bacteria that eat nitrite and convert it into nitrate. You get rid of nitrates by doing water changes.

In a new tank the bacteria is not normally present and you get a build up of ammonia that harms and can kill the fish. A few weeks after the tank has been set up, you get the first colonies of good bacteria that eat the ammonia. A couple of weeks after that you start to get the other good bacteria that eat the nitrite. It normally takes about 4-6 weeks for an aquarium to develop the colonies of good bacteria that keep the ammonia and nitrite levels at 0.

When the ammonia and nitrite levels have gone up and come back down to 0, and the nitrate levels start to go up, the tank will be considered cycled (developed the necessary good filter bacteria) and you can feed the fish once or twice a day and do a 75% water change once a week. Until then you keep feeding down and water changes up. By reducing the food going into the tank, you help to keep the ammonia levels lower. By doing big water changes, you help to dilute any ammonia in the water.

In a newly set up aquarium, you should feed the fish to 2-3 times per week. Don't worry, the fish won't starve. You should also do a 75% water change and gravel clean the substrate 4-8 hours after feeding. And you should monitor the ammonia and nitrite levels and do a 75% water change any day you have an ammonia or nitrite reading above 0, or a nitrate reading above 20ppm.

*NB* Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

The big water changes will not harm the filter bacteria or fish as long as any new water is free of chlorine/ chloramine before it is added to the tank.

-------------------------
During the first month of a tank's cycle, you monitor the ammonia and nitrite levels. You normally get ammonia readings for the first few weeks. The ammonia goes up and as the beneficial filter bacteria build up in numbers they gradually convert the ammonia into nitrite. After a few weeks the ammonia level will suddenly drop to 0 and the nitrite will start to go up. A couple of weeks later the nitrite levels drop to 0 and the nitrates start to go up. You get rid of nitrates by doing water changes.

During the cycling period you do not test for nitrates until the ammonia and nitrite have gone up and come back down to 0. Nitrate test kits will read nitrite as nitrate and give you a false reading. So you monitor ammonia during the first few weeks and then start monitoring nitrite as well. Once they have both gone up and come down to 0, you start monitoring nitrate.

-------------------------
Do not clean the new filter for the first 6-8 weeks. This allows the filter bacteria a chance to settle in properly and stick to the filter media. Two weeks after the filters have finished cycling, you can start to clean the filter.

Established filters should be cleaned at least once a month and every 2 weeks is better.

To clean a power filter or internal sponge/ box filter. You get a bucket of water from the aquarium and squeeze the filter materials out in the bucket of tank water. When they are clean you put them in the aquarium. Wash/ rinse the filter case and impellor assembly (for a power filter) under tap water. Remove any excess tap water by tipping the filter case upside down, then put the filter materials back into the filter and set it back up and get it going.

If you have an undergravel filter, that will be cleaned when you do water changes and gravel clean the substrate. You can buy a basic model gravel cleaner from any pet shop and they are worth getting. You only need a basic model gravel cleaner like the one in the following link. Do not buy the expensive fancy types because they are no better than a base model gravel cleaner.
https://www.about-goldfish.com/aquarium-cleaning.html

----------------
If you have a filter that containers pads/ cartridges that need replacing on a regular basis, do not replace them. Go to the pet shop and buy some sponge for a different brand of filter (I use AquaClear sponges but there are other brands), and use a pair of scissors to cut the sponge to fit in your filter. Keep the sponge and filter pads together for 2 months, then remove the pads and throw them away. Replace the pads with more sponge.

Sponges get squeezed out in a bucket of tank water and will last 10+ years.

You can also get round/ cylindrical sponges for some brands of internal power filter. These round sponges have a hole through the centre and they fit over the intake strainer of most external power filters. They add extra filtration and prevent small fish and bits of plant form being sucked into the filter.
Thank you. I have a water conditioner for water changes but I get concerned because it sets kh near zero. I will get an ammonia test kit asap.
 
I have never heard of a water conditioner that removes KH. Can you tell us what it is, either a link to the product or a photo of the bottle, please.
 
What water conditioner? They should have no effect on hardness.
 
Along with the requested data, we should also have a look at the numbers for GH, KH and pH of both the tap water alone and the tank water. Without this set of data we will not be able to fully sort this out.
 
https://www.aqueon.com/products/water-care/water-conditioners

That water conditioner doesn't say what's in it, but if it removes chlorine it will contain thiosulphate; if it removes metals it will contain EDTA.

It does say it 'helps restore the slime coat' which probably means it contains aloe vera, which we now know can coat the fish's gills.
It also says 'detoxifies ammonia and other elements that are released from fish waste'.

None of these things should affect KH.



KH does not directly impact fish the way that GH does. It is a buffer which prevents the pH from changing. If KH is high, the pH will not change (even if pH changing chemicals are added to the tank) but with very low KH the pH can drop when all the limited amount of KH is used up.


Can you look at your water provider's website and see if they give the hardness of your tap water. We need a number and the unit. If they also give something called alkalinity, tell us that as well, please. (Alkalinity is the term water companies use for KH)
 
https://www.aqueon.com/products/water-care/water-conditioners

That water conditioner doesn't say what's in it, but if it removes chlorine it will contain thiosulphate; if it removes metals it will contain EDTA.

It does say it 'helps restore the slime coat' which probably means it contains aloe vera, which we now know can coat the fish's gills.
It also says 'detoxifies ammonia and other elements that are released from fish waste'.

None of these things should affect KH.



KH does not directly impact fish the way that GH does. It is a buffer which prevents the pH from changing. If KH is high, the pH will not change (even if pH changing chemicals are added to the tank) but with very low KH the pH can drop when all the limited amount of KH is used up.


Can you look at your water provider's website and see if they give the hardness of your tap water. We need a number and the unit. If they also give something called alkalinity, tell us that as well, please. (Alkalinity is the term water companies use for KH)
Hardness 228 mg/L minerals 440 mg/L 7.8ph. I couldn't find alkalinity.
 
If you are in the UK, not many companies give alkalinity.

Hardness at 228 mg/l (assuming there was nothing after mg/l) is the same as 228 ppm. That converts to 12.7 dH. (Fish profiles use either ppm or dH so we need to know hardness in both)
This is hard, but not terribly hard so it is too soft for a number of hard water fish (if that makes sense).


Usually, but not always, high GH goes with high KH and vice versa.



When you say that the water conditioner resets your KH to zero, what exactly do you mean?
How are you testing KH - with a test strip?
Do you test the KH in the tank or in the new water you add at the water change?
 

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