Sudden Deaths of Apparently Healthy Fish

[hmskaggs]

I've posted a couple of other places about recently losing a fish. It happened about 3 weeks ago and both of the other fish in the tank seemed fine. With the other fish eating and behaving normally I just increased water changes and bumped the temperature a couple degrees (from 82.5 to 84). The fish that died was robust and eating well. Stools were normal and she had no external lesions. One evening she seemed 100% normal. The next morning she was face down at the bottom swimming in slow tight circles. Within a few hours she died.

Now comes my confession..... Out of a group of 5 juvies, she was my only female. As the group approached sexual maturity, lots of bickering ensued. I had already removed 2 subordinate males who had been getting abused. These I sent to my sister as I had no other available tank. It had always been my plan to grow out the youngsters until pairs began to form, then choose the best pair and sell and/or relocate the rest. With the two nicest males vying for her attention, I was just waiting for her to choose. The trio did well for awhile, but pretty vicious fighting between the males broke out suddenly one evening. It was late. Too late to make the one hour drive to my sisters and the only LFS still open had no tank dividers or partition material. What they did have was rummynose tetras on sale. So I decided in lieu of a partition, I'd go with dither fish. That's right, no quarantine. This trick worked beautifully to curb the fighting and I was pretty pleased with myself. We had 4 days of peace before the female dropped dead.

As I've already mentioned, everyone else seemed fine. The males continued to eat well. The rummynose looked great. Tank parameters were stable. Two weeks later, everybody seemed fine. I fed them around 2 pm, both boys ate well and behaved normally. At 8 pm I discovered the largest male head down on the bottom swimming in slow tight circles. The next morning he was also dead.

Both fish were necropsied and no gross abnormalities nor parasites were found. Gills were examined under magnification and were normal. So I panicked and treated the tank with two rounds of Parasite Guard. Again everyone seemed fine. "Surely that did the trick," I told myself. I began looking for a nice female to pair with one of the remaining boys. The last fish in the"infected" tank is my favorite. The other two boys were removed prior to introducing the tetras and appear healthy.

This evening the male in the "infected" tank began exhibiting some strange behavior. He seemed fine and was eating earlier in the afternoon. Then he began swimming somewhat erratically, pacing up and down the glass, and intermittently hanging out at the top. I fully expect him to be head down on the bottom swimming in circles in the morning.

The tank is 46 gallons. I use conditioned tap water with gh of 180 a kh of 20 to 40 and a pH of 6 to 6.5. Ammonia, nitrites, nitrates are all normal. Tank has been up and running about two years.

If anyone has any ideas about what I could be dealing with or recommended treatments I'd appreciate your thoughts. If the last discus in the tank is toast tomorrow, I'd like some advice on how to clean up the tank before any new fish go in. Thanks!

[hmskaggs]

Since no one has responded to my post I guess it's safe to say everyone's as baffled as I was. Anyway, I thought I'd post a followup in case someone finds this post while searching for a similar ailment. Response to treatment certainly isn't a diagnosis, but maybe it'll help someone. So the last fish in the tank survived the night but was nose up at the top of the water in a corner the next morning. He wasn't hypoxic. There were no rapid gill movements nor gulping of air. This fish was neurologic. Clearly not as severely affected as the others but definitely not in his head. In a last ditch hail Mary attempt, I began treatment with furan 2 and added salt (about 4oz) to the tank. 48 hours later there had been no change but he was hanging on. I did a 70% water change, added an appropriate amount of salt, and redosed with furan 2. The next day he looked a little better. He still spent a lot of time in his "spot," but he also swam around a bit and even ate a little bit of frozen blood worms. By day 4 (the final day of treatment), he looked almost normal. He was eating well and cruising around the tank but he still occasionally paced the glass. The next day (yesterday) I repeated a 70% WC, added more salt and some activated charcoal to the canister and you'd never know the boy was sick. Tomorrow I'll repeat the WC and salt routine and add some Turbo Start. I don't know what the issue was, but it seems to have been bacterial.