Corydoras Keep Dying, Most Times for Unknown Cause

[ella777]

It might be better to make your own thread about this, as it risks veering the OP's thread off-topic.

It is on topic though, it's about the same thing the person is talking about

 

[Bluejay72]

@ella777 It might be better to make your own thread about this, as it risks veering the OP's thread off-topic.






@Byron You know I respect your knowledge a great deal, and that zero nitrAte tanks are possible - but I also find it highly unlikely to actually be the case here, even with only 5-6 fish in 20 gallons, given that all but one of the plants visible are slow growing java fern and an anubius. One small fast growing plant and a java fern isn't usually enough to lead to zero nitrAtes, especially given that most people are inclined to over feed fish, and there's also a high risk of a filter being cleaned in tap water for example, and causing mini-cycles. Worth investigating.

ETA: @Bluejay72 along with your water changing/substrate cleaning schedule, can you also describe how and how often you clean the filter and filter material, please? Do you switch out new cartridges for example? Or rinse anything under the tap?

I never clean the filter material because I know there’s beneficial bacteria that grows there. I have a Fluval Aquaclear with the sponge and biomax. I replace 1 of the 2 every 45-60 days.

Water change is ~20% every 7-8 days on average with vacuuming the sand and around the plants where there’s a lot of detritus.

 

[Byron]

This [post #16] gives us more reasons, though here again I am not saying any one issue is "the" issue, but when something detrimental enters the tank it does impact the fish, and cumulatively this certainly does no good and it makes other issues far more impacting because the fish are being weakened with every negative, so to speak.

Never use any additive intended to kill something, unless it is a medication that is absolutely necessary to help the fish. Algae fix is likely a major issue here. Enough said.

Reason why any additive is dangerous if not deadly in time: Fish "drink" by assimilating water by osmosis through their cells. This continues pretty much all the time. This water enters the bloodstream and is carried to internal organs. There is also the water passing through the gill filaments. There is an exchange of substances here. Substances dissolved in the water that have the ability to diffuse across the cell membrane will thus enter the fish. The relationship of a fish to its aquatic environment is far more significant that that of any terrestrial animal for these reasons. So every substance added to the water is likely to get inside the fish. These are foreign substances, they do not benefit the fish in any way, but they do cause stress or worse, depending.

To the food. Shrimp pellets is a good food, but the Aqueon brand may not be. I cannot find the ingredients, presumably they are on the backside of the can. If they contain meals of fish or cereals they are not good, and also depends upon their protein level (low not high is best). Omega One Shrimp Pellets is one good brand. It is also lower (I suspect than Aqueon) in protein (36% if memory serves me) and this is important for cories that should not be fed high protein foods.

The Hikari sinking wafers are definitely not good for cories. Here are the ingredients:

Fish meal, wheat germ meal, soybean meal, wheat flour, whole crushed silkworm pupae, dried seaweed meal, dried bakery product, brewers dried yeast, fish oil, krill meal, spirulina, garlic,...​

This is awful stuff. Fluval Bug Bites is considerably more nutritious. The prime food of Corydoras fish is insects and insect larvae, followed by crustaceans. Bub Bites and Omega One shrimp pellets as basic foods. Fresh frozen as treats is OK, daphnia, shrimp.

 

[Byron]

I never clean the filter material because I know there’s beneficial bacteria that grows there. I have a Fluval Aquaclear with the sponge and biomax. I replace 1 of the 2 every 45-60 days.

Water change is ~20% every 7-8 days on average with vacuuming the sand and around the plants where there’s a lot of detritus.

Do not replace the media, rinse it under the tap as often as you need to. All that brown gunk is detrimental to fish. You have plants, and less than half a dozen small fish. The filter only has one task here, to move the water. Keep it clean, but replacing the foam. etc is only taking your money.

I already noted water changes need to be larger, 50-60% once a week. As you have cories, it would help to clean into the open substrate areas.

 

[Bluejay72]

This thread has become significantly hijacked, so going forward I will only be responding to the OP's questions/issues. Otherwise it will get hopelessly tangled and be of little value to him/her.

GH, this is good, no issues there.

Ammonia, nitrite, nitrate at zero are excellent. No issues here.

Water conditioner...Do not use StressCoat, it has aloe vera known to affect fish gills. You only need one conditioner anyway, one that detoxifies chlorine/chloramine (usually) and heavy metals. Personally I would not use Prime, it messes around with other things best left alone. The API Tap Water Conditioner is probably the best we have. I am not saying this is causing cory deaths, but I am saying this conditioner is not as good as many think, and the TWC is preferable and safer (I could go into details over what is in Prime but it would hijack the issue more, so not needed).

Shrimp Essentials...not sure what is in this but I assume it is some sort of mineralization for shrimp. I would not use this in a tank with cories. There are soft water shrimp you could get. Cories will consider shrimp to be food (it is their second most natural food in the habitats, after insects/insect larvae). Having said this, I do agree this is not likely the issue, but once again it is best avoided.

Increase the volume of each water change to at least 50-60% of the tank volume (at one change, not spread out). Do a good clean into the open areas of the substrate. Sometimes clean water does wonders.

Everything is looking pretty good, but I am still questioning the wood...those lightish patches I can see, you are certain they are not a bit slimy? I can only go from photos and often it is not the same as seeing it "live" as it were.

You did not mention the foods you are feeding them. This is important.

It is always possible the fish have something from the store, you did say there was a dead fish in the tank. I would check to see if the cories left in the store are having issues like your fish.

How long should I be doing large water changes? Permanently? Or for a set time period?

 

[Byron]

How long should I be doing large water changes? Permanently? Or for a set time period?

Permanently. I have an article here on the importance of regular water changes:

Regular Partial Water Changes

Byron Hosking November, 2010 (rev April 2021) Nothing is more important when it comes to aquarium maintenance than regular partial water changes. The adage “an ounce of prevention is worth a pound of cure” certainly applies here. One frequently reads of products that will reduce the need for...

www.fishforums.net

 

[Bluejay72]

This [post #16] gives us more reasons, though here again I am not saying any one issue is "the" issue, but when something detrimental enters the tank it does impact the fish, and cumulatively this certainly does no good and it makes other issues far more impacting because the fish are being weakened with every negative, so to speak.

Never use any additive intended to kill something, unless it is a medication that is absolutely necessary to help the fish. Algae fix is likely a major issue here. Enough said.

Reason why any additive is dangerous if not deadly in time: Fish "drink" by assimilating water by osmosis through their cells. This continues pretty much all the time. This water enters the bloodstream and is carried to internal organs. There is also the water passing through the gill filaments. There is an exchange of substances here. Substances dissolved in the water that have the ability to diffuse across the cell membrane will thus enter the fish. The relationship of a fish to its aquatic environment is far more significant that that of any terrestrial animal for these reasons. So every substance added to the water is likely to get inside the fish. These are foreign substances, they do not benefit the fish in any way, but they do cause stress or worse, depending.

To the food. Shrimp pellets is a good food, but the Aqueon brand may not be. I cannot find the ingredients, presumably they are on the backside of the can. If they contain meals of fish or cereals they are not good, and also depends upon their protein level (low not high is best). Omega One Shrimp Pellets is one good brand. It is also lower (I suspect than Aqueon) in protein (36% if memory serves me) and this is important for cories that should not be fed high protein foods.

The Hikari sinking wafers are definitely not good for cories. Here are the ingredients:

Fish meal, wheat germ meal, soybean meal, wheat flour, whole crushed silkworm pupae, dried seaweed meal, dried bakery product, brewers dried yeast, fish oil, krill meal, spirulina, garlic,...​

This is awful stuff. Fluval Bug Bites is considerably more nutritious. The prime food of Corydoras fish is insects and insect larvae, followed by crustaceans. Bub Bites and Omega One shrimp pellets as basic foods. Fresh frozen as treats is OK, daphnia, shrimp.

Thank you so much for your very detailed response. This makes a lot of sense. I look at ingredient labels for myself, I really should have been doing the same for my fish. I will change what I’m feeding them.

Does it look like I need to use blue green stain remover (pictured below)? Or is this an unnecessary and potentially damaging addition to the aquarium?

 

[Bluejay72]

Permanently. I have an article here on the importance of regular water changes:

Regular Partial Water Changes

Byron Hosking November, 2010 (rev April 2021) Nothing is more important when it comes to aquarium maintenance than regular partial water changes. The adage “an ounce of prevention is worth a pound of cure” certainly applies here. One frequently reads of products that will reduce the need for...

www.fishforums.net

Great, I will take the time to read this.

 

[Byron]

Thank you so much for your very detailed response. This makes a lot of sense. I look at ingredient labels for myself, I really should have been doing the same for my fish. I will change what I’m feeding them.

Does it look like I need to use blue green stain remover (pictured below)? Or is this an unnecessary and potentially damaging addition to the aquarium?

If any substance goes in the water, it has the potential to harm the fish. Even "beneficial" substances like water conditioner will be harmful if we use too much. And no substance that is not going to help the fish should ever be added, period. Certainly nothing that has the potential to kill something, be it algae, cyanobacteria, or snails.

 

[Bluejay72]

If any substance goes in the water, it has the potential to harm the fish. Even "beneficial" substances like water conditioner will be harmful if we use too much. And no substance that is not going to help the fish should ever be added, period. Certainly nothing that has the potential to kill something, be it algae, cyanobacteria, or snails.

Thank you! I will never add anything except for medical treatment when absolutely necessary. Otherwise, I won’t add anything at all.

 

[Byron]

Thank you! I will never add anything except for medical treatment when absolutely necessary. Otherwise, I won’t add anything at all.

Good plan. Sometimes we may need plant fertilizer, this too can be harmful depending upon the species, but provided it is kept minimum it should be OK.