Pedro111

My fish are dying, and I don't know why...

After fishless cycling, I introduced my first couple of fish into my 77 gallon planted tank: 2 red lizards (L10-a). They settled in fine. No ammonia or nitrite readings, and low (<5ppm) nitrate after 3 days, so I introcuded three new occupants: 3 Mikrogeophagus ramirezi. They were still pretty young (the shop didn't have any full-grown ones), so I'm not too sure about their sex. They were doing ok for the first 2 days, being shy but not overly so.

On day 3, I suddenly couldn't see any of them any more.

I figured they had gone ultra-shy on me (there's a lot of hiding places in the tank), so I decided to add some more fish to draw them out a bit. Note that ammonia and nitrite were still 0 at this time, with continued low nitrate readings. I bought two dwarf gouramis (two males - the shop didn't stock any females, sadly) and 4 Corydoras julii.

One of the two dwarf gouramis was very active from the start, busily exploring every nook and cranny. Lo and behold, it wasn't too long until I saw the first ram. It did, however, not look good. I couldn't see any external signs of disease (no blotches, fin rot, fungus, patches or anything), but he/she was clearly suffering: very laboured breathing, hardly swimming at all, and often toppling over sideways.

The following morning, the fish was dead. That afternoon, I saw a second ram. Same symptoms. Died that evening. I never saw the third one.

I rushed to the fish shop and bought Myxazin, as I suspected a bacterial infection.

While all this was happening, the active dwarf gourami, the corydoras, and the red lizards all seemed to be perfectly healthy. The big red guy was eating everything he could get his mouth on.. but he was also being a bit of a bully (right from the start) and attacking the other (slightly smaller and far more subdued) dwarf gourami, who spent most of his time hiding in the plants.

On the day after the two rams died, the poor hiding gourami started developing some of the same symptoms. No external signs, and the colouration remained beautiful, but he was having trouble keeping his balance and kept dropping.

The following morning (today) he too was dead. I looked at his body closely, and everything looked fine. No blemishes whatsoever. Just death.

I'm on the third day of dosing Myxazin, and all the other fish look healthy without any symptoms at all, behavioural or otherwise. Water chemistry is fine (NH3 0, NO2- 0, NO3- 5, pH 7).

Before I introduce any new fish, I would like to know: what's been killing my pets?

Thanks,

Pedro

Amanda

Were they all bought from the same store? They may just have weak specimens for sale, I've definently seen that happen

Red1313

Hmm... to be on the safe side I'd QT your new stock for 4 weeks before you add them to the aquarium, this way you have 4 weeks to ensure that your main tank is healthy and that the new fish are as well. (Also if the gourami is being a bully I'd take him out, add the new fish, wait a little while for them to settle in then add him back when you go to add the new ones.)

Pedro111

Thanks Amanda. The rams were all from the same shop. The gouramis were from a different one. I'd like to think that they were both from weak stock (quite common here in SE Asia, from what I hear).. at least that would make me feel less guilty about that mini-genocide.

Red, thanks for the ideas. Unfortunately, I don't have a second tank at the moment - though I should probably consider getting one.

Red1313

Do you have a large rubbermaid tub or plastic container of some sort? You don't need an actual tank for QT just something large enough to do the job for a few weeks. Rubbermaid containers are great for it but any sort of tub or container that you can add a couple sponge filters/filters to works fine.
I know there's a great thread hidden on the forum somewhere called a "quick and dirty QT tank" I believe.