sick cardinal tetras

[OfficeFish]

I have about 10 cardinal tetras that are starting to lose their scales, some have tumors on their tails and one can't close it's mouth. :eek: Are they sick? Is it old age? They were adult sized when I bought them 1 year ago - how long to tetras live? Help!!

Here's tank stats:

80+ gallon community tank (second hand)
Ammonia 0
Nitrites 0
Nitrates 40 (have plants)
pH 6.5
Temp 82F
Water changes 20% weekly
12 angelfish + 1 zebra danio

The same fish have been living in the same tank for the past year without any problems. What can I do to save the little fish?

[VoodooChild]

Thanks for the info. Tank specs make everything much easier. I'd do a few 20%'ers, maybe once every two days, until the nitrates get lower. 40 ppm isn't anything to be worried about, but every ppm is that much more stress on the fish. Try and stay below 20, but that isn't really the issue at the moment. When you say tumors, do you mean distinct tumors, like large bulges at the base of the tail? I've never heard of more than one fish having a tumor at a time. A bit more detail here could help make a better diagnosis (or as best we can over the internet). As far as scale loss goes, it's more than likely something is beating up on them. Watch them for a bit. It may be one of them, sharp rocks, something else, etc. Tuberculosis has similar symptoms but is pretty rare. Something to watch out for though. I'd watch the fish for awhile to make sure that something is beating up on them. Check for skin parasites as well. Watching these guys, particularely up close, will take some patience. And as far as a mouth problem goes, it's jaw may have been locked open, which could be caused by the same thing that is causing the loss of scales. I can't think of what else would do that. Hope this helps!

[OfficeFish]

Thanks Voodoo.

There aren't any visable external parasites and there is definately a tumor-like growth on the tails of 5 (or 6) tetras. The tumor is relatively round, lumpy and is located on the very end of the tail where the tail fin starts. It's not BIG, maybe a medium sized tumor, doesn't inhibit movement but definately larger than their original tail size. Gosh I hope it isn't TB.

There's a bunch of tetras that are perfectly healthy too (around 8 or 9 healthy ones) :confused:

The tetras are peaceful. Kinda boring. They don't fight each other and the other tank mates ignore them. I only have potted plants and "plastic moss" that covers the bottom of the tank. No rocks or other ornaments to cause injuries....

They are eating extremely well - they feed on angelfish eggs once a week when the angels spawn!:p