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Hi, Folks:

Before new year, I bought 10 panda corys from my LFS because of holiday discounts and the availability of a 20 gal tank. The 20 gal tank has 5 small swordtails and 2 one inch flying fox. Within 3 weeks, I only have 3 left now. I tested the water with API Ammonia testing kit. There was no trace of ammonia according to the API test kit, and the water temperature was around low 70F. Water is around 7.6 ph. I changed the water 10% frequently within a couple of days. The water before going into tank has been sitting for at least two or three days in plastic water jugs. I have a AquaClear 200 external filter and air pump. There is no sand bottom but have three small Ziggy's food containers to grow plants. They are fed with Omega sinking food sticks and various kinds of flake.

After a while, I notice that some of the corys were thinning out. If you look from the top, their stomach area look normal, but the rest of the body look very thin. They seems swimming a lot, up and down the glass. The three left have even body distributions and slight large stomach area.

I suspect that they were not eating enough. Therefore, I put the 2 or 3 food sticks into the tank when I turn the light off. I usually feed them twice a day. I visually examine their bodies, and their barbels were still there. No ick on the fin. No cloudy eyes.

The swordtails are doing very well that they have two babies.

Any suggestions for me? Thanks.

Philip

Do the Corydoras have and red on the belly area? You may be dealing with bacteria growing in the slime that accumulates on the bottom of a bare-bottom tank. I would try a thin layer 1/4 inch or so of sand.
It sucks that you lost a bunch, but focus on saving the last three. And make sure no other fish are bothering or stressing the Corydoras.

Hope that helps

Hi Panda,

Welcome to PlanetCatfish.

As for your fish problems, in addition to the possibility of bacterial infection, I can think of a few other issues to consider.

1. You say you got the tank before New Years, and it's been running about 3 weeks. You say you tested the water for ammonia and there was no trace of ammonia in the tank. However, what you don't tell us is when you tested for ammonia or how often you ran the test: If you tested only recently and your result was "trace," it doesn't guarantee that your fish were safe from ammonia. It takes about 3-4 weeks to start a brand new aquarium using new equipment (filter, substrate, decorations, etc.), while your tank grows or "cycles" the beneficial bacteria/microbes in the water that remove ammonia and convert it (via nitrite) to nitrate, which is less harmful to fish, but still not good.
   
   If you tested for ammonia only recently, then yes, your tank should by now have enough bacteria to metabolize the ammonia and remove it. However, during those first three weeks the bacteria were missing, so in that time you may have had ammonia spikes which would be harmful to the fish. But at this point in time, now that the bacteria should be present, the ammonia will have been removed for the most part, and you won't find much.
2. You don't mention if you tested for nitrates or nitrites in your water. Nitrites are really harmful, nitrates are less-so, but still bad.
3. You also mention that you performed a 10% water change "frequently within a few days" - within a few days of what? When did you start the water changes? If only recently, after your fish started to die, then the problem already exists. But even if you started doing water changes immediately, I don't know that a 10% change is going to do much good. Think of it this way: If your tank has ammonia levels of 2 ppm (which is high), and you change 10% of the water, you only remove 10% of the ammonia, and you leave 90% of the ammonia behind. So even AFTER the water change, your ammonia readings will still be 1.8 ppm, which is still high.
4. About aging the water. The main reason for aging the water is to allow any chlorine added to your water to evaporate out into air, making the water safe for fish. If your jugs were sealed (you don't mention either way), this isn't as effective for chlorine removal. If your city water supply is treated with chloramines instead of just chlorine, "letting the water age" will not remove the chloramines. For these chemicals, as far as I know, the main way to treat them is with a product like SeaChem Prime, or NovAqua (there are a few more of these), water treatment chemicals that specifically say they neutralize chloramines. These will also take care of chlorine too.
5. One last thing to consider - what kind of pet store sold you the fish, and how healthy did they look when you bought them? If you bought them from a chain store, often times the fish can be sickly to start, even if they don't look it.

I'm not sure what else to suggest you consider. I wish you the best of luck with the remainder.

Cheers, Eric

Thank you for the ideas. I will try to tackle the water quality problem. I suspect that the water utility may have been added more chemical into the water since the new year. There were snow melting on-and-off in my area after new year. However, my angels and pleco were not affected.

Their belly looked ok but their bodies looked pretty thin.

Thanks.