All Albino Cories Getting Sick Or Dying In The Tank

[SouravBanerjee]

Hi all,
 
We have a 3.5 g tank. We do a weekly 25% water change. Water quality seems to be absolutely fine (ammonia, nitrates, nitrites, pH, hardness, etc). We have two balloon bellied mollies and two albino cories. The albino cories kept getting sick (red sores, fin rot, redness all over lower part of their bodies), despite our best abilities to keep the water and tank clean. We quarantined both the cories, and they recovered with antibiotics. When we introduced them back into the tank, they immediately exhibited redness in the lower bodies within half an hour. Then one eventually died. We again quarantined and treated the other one back to recovery, and again tried to introduce him/her back into the tank. Within 5 mins of introducing, it  exhibited redness (like sores) in the lower part of the body. The cory does very well when separated from the tank ( was absolutely ok for one week in separate tank). We've tried everything, but we can't seem to pinpoint what's going wrong. Can anyone help with what's the problem? 

 

[fluttermoth]

Could you post the actual numbers from your tests, please, along with details of what tests you're using?

What substrate do you have, and do you make sure it's thoroughly cleaned when you do your water changes?

How long has your tank been set up and how was it cycled?

Sorry for all the questions, but the more details we have, the quicker we can get to the root of your problem.

I will say one thing right now; I'm afraid your tank is far, far too small for the fish you have. Both mollies and albino cories grow to around three inches long (the mollies possibly larger) and a 3.5g tank just isn't large enough to house those fish comfortably or healthily.

There's also an issue of water conditions. Mollies need hard (or even brackish) water to thrive, while cories, although some species are relatively adaptable, do better in soft water. One or other species is not going to do well.

In addition, corydoras are very social fish, which should never be kept in groups of fewer than six.

 

[FroFro]

As the above poster said, can you list exact numbers for us?
 
A 3.5 gallon tank is too small. Fish require at least one gallon per inch of fish, so if you have two full grown cories at around 3 inches you need 6 gallons and even more would be better for optimal living conditions.
 
Have you treated the main tank? If you are quarantining one and then returning it to the same tank and its still getting sick the problem most likely is something IN the main tank. Small tanks that are filled beyond capacity can accumulate filth quickly and are harder to maintain, raising stress levels for the fish inside and resulting in health issues. Mollies can also be territorial and nippy if not kept in larger groups/ with at least one female or are in closed quarters/ feel over crowded. I used to keep mollies and learned the hard way they will bully other fish. Have you done larger water changes, cleaned your ornaments and given your gravel a good vacuuming? Have you perhaps treated the main tank already and not changed the activated carbon/ didn't remove the filter media before treating? Meds tend to kill off the beneficial bacteria so this can also result in water quality changes. If you don't have a larger tank or can't afford one I highly suggest rehoming some of your fish or even getting a very large/deep tub with clean treated water and adding a water heater to at least give them more space until you figure out what is wrong.

 

[StevenF]

 
 
Water quality seems to be absolutely fine (ammonia, nitrates, nitrites, pH, hardness, etc).

Idealy your ammonia and nitrite should be zero.  nitrate 20ppm or less.  with your stocking level and the sizeof your tank I find it hard to believe everything is absolutely fine.  I would like to be wrong but I don't see how you can do it in a 3.5 gallon tank.  Also a 25% water change once per week is probably not enough to keep nitrate and phosphate levels low.

 

[BeckyCats]

Like fluttermoth, I was going to ask about the substrate. Corys need sand, so I am wondering if your sick tank might be bare while your main tank could have gravel. Just a thought since we don't know the answers to the questions above.

Also, I agree with everyone else that your tank is too small to be humane for your fish. Not trying to criticize or judge at all, just looking out for the best interests of the fish, as I'm sure you are as well. This site is great because we all learn from each other.