Harlequin Rasboras wasting away

[spikeIt]

Hi. Currently I have a 29 gal tank with 2 ottos and 4 Harlequin Rasboras. The Rasboras were originally a group of 5 I added about 6 weeks ago. Each rasbora was approximately 1/2" in size. The ottos have been in residence for several years.

I euthenized one rasbora a couple weeks ago as it was wasting away and was having trouble swimming. It was still eager to feed, but upon staying stationary, it couldn't keep its head upright and was subtley rolling in the water. Also, its back end to the tail seemed to be thinning and shriveling. I didn't think there was much chance of survival so I took action to avoid any feeding on him.

At that time, at least a couple more of the rasboras were showing a little color fading and I had thoughts they might be ill as well. This weekend I returned from a weeks vacation (some friends fed them a couple times), and two of them look to be degenerating in the same manner as the first rasbora. Both seem to be thinning in the tail end of the fish. Again, all four are eager to readily feed and none seem to have any problem holding the food down. But I'm noticing the same head first rolling problem when stationary and the faded color. The other two rasbora look and seem to behave fine. The healthy two swim together, while the sick ones seem to isolate themselves when not feeding.

I've looked through a Fish Health manual I have, but I can't really find anything to relate to their problem.

The ottos, when I see them, look and behave as usual.

Does anyone have any idea what could be afflicting the fish? Could this be similar to neon tetra disease? Any course of action possible?

Current tank specs are:
29 gallon
Temp ~79 F (its summer here)
pH 7.2
Ammonia and nitrites are zero
Nitrates are around 15
GH 4, KH 3

Thanks in advance.

 

[OrionGirl]

Sounds like a bacterial infection of some kind. I would remove the fish and treat them with a medicated antibiotic, broad spectrum (gram + and - if available). Contact the LFS, and see if they've gotten any reports of problems with this batch of fish as well.

 

[spikeIt]

Oriongirl,

Thanks for your quick response. Unfortunately I don't have anyplace availabe to isolate the sick fish and I'm reluctant to use antibiotics on my main tank as I believe it would kill any bacterial colony I have in my filters. A foolish move on my part, but in my haste to finally get something going again in my 29 gallon, after adding this batch straight to it, I added a different batch of fish into my QT.

Anyhow, one of the two sick fish did die off about 3 days after my original post. The other is hanging on, but I imagine it won't be much longer now. The remaining two rasboras look perfectly fine and the ottos I find to be impossible to harm. As sad as it is, I think I'm going to let things run their course for the one fish and let the tank stay isolated for a month afterward to make sure the other fish don't pick up whatever this is.

Anyways, thanks again. Next time I'll be sure to keep my QT tank free so I can try out some medications. In the past I haven't really had luck medicating fish, beyond curing Ick. Diagnosing fish diseases seems to be very much a guessing game.