I have a normal community tank with:
glowlight tetras, neon tetras, black phantom tetras, 1 catfish, 1 up-side down catfish and 2 dwarf gouramis.

The female dwarf gourami has had her fins nipped and are becoming dangerously bad. Also the black phantom tetras are at deaths door due to there fins being eaten away.

None of the other fish show any signs of fin damage.
I have treated the entire tank for fin rot, to no avail.

All of my fish are supposed to be friendly un-aggresive fish, and I have carefully watched the tank for signs of a culprit, but nobody seems to be up to any mischief (although occasionaly the male dwarf gourami can get a tiny bit aggressive, but inly for a few seconds).

PLEASE, can any body help. Am I doing something wrong?

I (myself) cannot rule out an aggressive fish in that group, but I can say that if the general water quality is bad, your fish’s fins will become torn and tattered. Did you test for Ammonia, Nitrites, and Nitrates? This probably wouldn’t hurt, in fact it would rule out whether or not it is your water quality that needs improving.

What size aquarium do you have? Can you explain the patterns in which you clean your aquarium (how often, how much water is drained each time, etc.)? Are you using any water conditioners?

It could be a water quality or illness issue but the fact that only certain fish are being torn seems to indicate that it is due to fin nipping. What kind of catfish is it? Of the fish you list, I've not know neon tetras, glowlight tetras, or upside-down catfish to be fin nippers. Male dwarf gouramis and black phantom tetras can be so I would guess (if there's nipping) that one of them would be responsible. I don't know about the catfish because you don't say which kind it is. If only those fish with long fins are being targeted, that could indicate that the culprit likes to bite long fins or that the fins are simply more apt to be injured (sucked into a filter or just ripped from other things) or infected by fin rot. Fin rot usually causes the fins to have a white edge that rots away and not actual rips. It's also possible that the male gourami is nipping the female (common if he is ready to breed) while the black phantom tetras are nipping each other. Observe the tank for longer periods of time, and you should be able to figure it out. If it is nipping, you can move some fish to another tank, put the culprit into a net breeder (confinement, not good long term), or just put in lots of places to hide (ornaments and fake plants) and hope they learn to get along.

Thanks a lot guys, thats helped out quite a bit!!! I wasn't aware that the black phanton tetras could become aggressive.

To answer your questions:
I have tested all my levels and the nitrite is zero, nitrate is about 5 ppm and ammonia is also zero. I have a 50 gallon tank and perform a clean every week. I take aprox. 1/4 of the water, basically, enough to clean all of the gravel and ornaments.
I am using a water conditioner, and to my knowledge it is just an every day water conditioner/de-chlorinater recommended by the fish shop.


The catfish that I have is a Sailfin Plec (Glyptoperichthys gibbiceps), but he always seems to be just stuck on the side of the tank, minding his own business.

I have just purchased some more ornaments as I actually thought about more places to hide, so I can see how we get on.

The fins on the Gourami are not torn, they do have a slight fluff to the edges,which would point to fin rot yet I have seen the male nipping at the females fins. The commercially available fin rot treatment I have used doesn't seem to have done anything, any ideas?

I did catch two black phantom tetras bickering last night, and looked as if they were getting quite aggressive, is this kind of behaviour normal?

Once again thanks a lot chaps! Much appreciated.

The sailfin plec shouldn't be a problem then, and your tank situation sounds fine.

The female gourami may be getting small nippings or harassment from the male which then provides an injury site for some fin rot. Fungus and bacteria will take advantage of cuts and wounds to attack. If you don't have aquarium salt in the tank, a little might help. The catfish and tetras don't like a lot of salt but most fish can tolerate a little. Just a tablespoon per 5 gallons will help repel the bacteria and fungus on injured fins. You might also add MelaFix by Aquarium Pharmaceuticals which is all natural and aids healing. If the fin rot, fungus, or bacteria on the injured fins gets bad (really fuzzy, falling off, etc.), then the fish should be quarantined and treated with antibiotics and/or anti-fungals depending on what happens.

Provide a lot of places to hide and that should help a lot. They sell all sorts of live and fake bushy plants.

It is normal for phantom tetras to be nippy, especially with each other. I've never had them but have read that from more than one source.