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We've recently noticed some sort of problem in a 55 gallon South American tank. Among other fish in the tank, there is a <i>Pimelodus ornatus</i> and a <i>Pseudocetopsis</i> sp. These two fish, which used to be the most reclusive in the tank, are now acting oddly and swimming aganst the current provided by a power head. No signs of ich or velvet, and the only thing out of the ordinary is the two fishes' thicker than usual slime coat. The ornatus' barbels are also withering. Nitrite and ammonia aren't present, and pH is at about 6.4. Filtration is provided by a Eheim 2215 and a Penguin 660 with a prefilter sponge attached.

What should my course of action be? If it gets any worse, I'll quarantine the fish, but right now I don't want to stress them out any more than they are right.

Rusty

Rusty,
Sounds like the gills are infected with parasites. I use a five minute dip in Formalin. Mix 20 drops of Formalin in one liter of water and dip for five minutes. This treatment has worked very well for me in the past and I use it on all newly captured loricariids before placing them in quarantine.
-Shane

Didn't have any formalin handy (not something you'd want to use around little children) so I've started to bathe them in Seachem ParaGuard, which lists its active ingredient as aldehyde (10%). If that doesn't work I'll try and get some buffered formalin from AMNH.

Rusty

Rusty wrote: Nitrite, ammonia, and nitrate aren't present, and pH is at about 6.4.

Rusty, just check the sell-by on your test kits. It's a very unusual Freshwater aquarium that doesn't have any Nitrate, even if only 10 ppm or so.
Next, has anyone close by had any chemical treatment done to their house/apartment/whatever that could have come through ventilation ducts?
The only reason I'm saying this is because the symptoms could be of chemical poisoning instead of a parasitic infestation (have you actually introduced any new fish to the tank recently?).
What day was your last water change? (I've known people have trouble with Cats through something nasty in the water supply following a water change).

My last water change was on the 16th, but I think that the cetopsid may have been showing symptoms before then.

All the other fish in the tank (a bunch of lories, some chilos, a few banjos and some cories) are out and about, but I fear that this may change soon

Rusty

In fact, we did not test for nitrate. (Just a little bit of adolescent exuberance there! Excuse us. ) The nitrate level must be in the 50-100 mg/l range. This is what it has typically tested at when we last tested (a fairly long time ago). Not low, but not high enough to cause a problem.

I don't think I've seen this problem before. Something is definitely amiss, but I don't know what. The affected fishes are out in the open, so I was able to examine them with a magnifying glass. Didn't see any visible pathology, except for some shriveling of the tips of the P. ornatus' barbels.

Acting on Shane's advice, we did a one hour bath using Seachem ParaGuard. It may have helped, but the fish are acting as they did before.

We'll keep you posted.

the first thing that crossed my mind when rustam told me was to maybe try the timbeer garlic therapy (http://forum.planetcatfish.com/viewtopi ... ght=garlic) i had sth similar a while ago and treated for gillworms with sth called preis coly (or sth like that cant remeber) maybe it was this or not but it got better afterwards.
good luck

Does anybody smoke or use aerosols in the house? We have had fish poisoned this way in past.