Quote Originally Posted by wh33t
Interesting! I'll have to try adding a light. Do you know what the deficits are from not having a light cycle? My fish are just goldfish, so they are not for eating.
From what I understand, they just grow slower. Spawning could be another issue depending on the species. Some fish may have problems with no light, but I don't know any offhand.

I have about 2 dozen goldfish that are practically sealed up and have not seen "the light of day" for almost a year (besides feeding time). Maybe fish that are naturally "bottom dwellers" would be less affected? But yea, you just want your fish to poop; so, light may not be an issue for you. I hate to tell you, but it is definitely something else... they're either sick or the water quality is poisoning them. What's your water like? Any signs of problems on the fish? How are they acting? Does your tank smell or taste funny?