11-17-2008, 06:41 PM
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Sudden Bacterial Bloom on Established Tank + Fish Deaths
My 20g tank went from perfectly smooth to disaster in the space of a couple of hours while I wasn't around. The tank contained 6 tiger barbs, 1 dwarf puffer and 1 clown pleco. So far, one barb (the dominant male) and the puffer have died. The water went from crystal clear to a watered-down milk color within the space of hours, which screams bacterial bloom to me. Tank maintenance is always done regularly so I don't always do regular testing, but of course I tested the tank right away. No ammonia, no nitrite, 10 ppm nitrate but I did a 50% water change just to be sure. Post-change there was no ammonia, no nitrite and 5 ppm nitrate. The fish were gasping at the surface. The tiger barb died this morning, and the puffer died about an hour ago. I just did another 50% water change but the water is still cloudy.
What could be the reason for this bacterial bloom? The parameters are all in check. The only thing unusual I noticed is that the driftwood started to grow some weird white slimy mold stuff, which spread to the filter intake right before the bacterial bloom. Could this be related?
So, my questions are: can I assume that if my water parameters all checked out that the fish died due to oxygen depletion because of the bacterial bloom? Also, what could be the cause of the bloom? These fish haven't been overfed and like I said, I'm pretty anal about tank maintenance and water changes. Is there anything I can do to halt it? The water change last night cleared the water up a bit but it was cloudy again today, so these bacteria are still multiplying. I did a bit of research but all I could find on bacterial blooms was related to new tanks and escalated ammonia levels.