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13 Posts
Discussion Starter · #1 ·
Greetings to all.

This past Sunday we found 4 dead demasoni in the tank. I removed them, and did a 30-40% water change. (I normally change water every two weeks on Sunday, and this was a 'non-maintenance' Sunday). Monday, came home form work and 2 more dead. Did about 60% water change. Today (Tuesday) just found 2 more dead. Only demasoni are dying.

Before you all ask, here's the 411 -
90 gallon stocked with:
20 Ps. Demasoni [make that 12 now]
11 L. caeruleus (Yellow Labs)
4 Synodontis petricola (Catfish)
2 Ps. acei (Ngara

Tank was set up in December of 2007 and all species were 1 1/2 to 2 inch at the time.
Water parameters:
pH 8
temp 80 F
Ammonia 0
Nitrite 0
Nitrate 10-15ish
Food: NLS pellets, 1x daily at 6pm (yes, everyone still has/had good appetite)
Behavior: normal (nobody at the bottom, breathing heavy, agressive, stressed, no bloat, no ich, etc.....)


These fish are just plain dying mysteriously and randomly.
Yesterday, my biggest and prettiest demasoni was one of the casualties.
Today, one of the most aggressive ones died. (note that I have never experienced aggression issues to date.)
None of the dead fish are missing gills or fins, or eyeballs, etc. they are just dead.
Some were smaller, some were bigger.
None (dead) were holding (two demasonin are still currently holding)

There is nothing abnormal in the air quality.
No changes in the tank setup.

If anyone has any advice, please help.

I have read multiple discussions on this forum, and have found nothing that directly concludes an issue in my situation.

Thank you in advance for your advice and suggestions.

(also note that I have experienced both ich and bloat in the past and none of the fish are symptomatic for either of these ailments)

239 Posts
I also had a mysterious disease killing off my fish, in which they too had no visible symptoms. I lost about 12 fish in total before I finally got some advice and used it. A Fish store owner had told me they most likely had bloat. He said sometimes they don't show very many symptoms at all. So I treated with metronidazole, and have not had any more die since. I would honestly try treating them for bloat first, and see what that does. As well, my best recommendation for africans is to do weekly wc's of 25% rather than large wc's every 2 weeks. Some fish like discus can tolerate large water changes better than others. And for africans, smaller more frequent water changes seem to do better for them.

18,306 Posts
First off, thank you for providing so much information! :thumb:

How much do you watch the tank? None of the fish that died were exhibiting any unusual behaviour prior to their deaths? Everyone was eating up until the end?

With sudden deaths like this, when you know it's not the water and you rule out everything else, you have to look at aggression, especially with the other species NOT being affected.

I would guess that you wound up with an unusually heavy male load. Since there has obviously been spawning activity or you wouldn't have two holding females, it's likely that all your demasoni are maturing at once and things aren't working out too well.

I know that everyone says the male / female ratio isn't important, but I do believe that when you do get really unlucky and wind up with too many males, things like this will happen.
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