I have a 29 gallon tank that has been up and running for 3 years. The underlit suggestion just may be the problem as now that you mention that I think it may have started after I had replaced my bulb. I have a 20-40 whisper filter, and air stone running all the time also.
I have 6 rasboras, 1 swordtail, 2 small tetras, 1 cory and a small pleco and feed them tropical fish flakes twice a day, about as much as they can eat in 2 minutes or so but also toss in a couple of shrimp pellets as the pleco and cory seem to devour them.
The bulb that came with the tank (which was the 29 gal
. kit from Walmart) was replaced with a 50/50 (50percent natural 50 percent actinic 03 blue) 20 watt bulb.
If this is due to low lighting, what do all of you suggest. Thanks so much for your help!