Black molly died, fish acting strangely.

Question
We have two pearl gouramis, one chinese algae eater, two red finned sharks, one goldfish, five mollies (two juvenile dalmations, one orange, one black, and one sunburst sailfin male) and a fiddler crab. We also have a variety of live plants. Our newest additions are the gouramis and the male sailfin, which were added last week. Yesterday I noticed most of our fish grouping together in corners of our 29 gallon tank. All except for the gouramis are lethargic and hold their fins in tightly. Then, this morning I found our black molly dead. I tested the water for pH, nitrites, ammonia and chlorine, and all were normal. We've had the black molly since September. Yesterday I did notice that 3 or four little greenish egg things came out of her, which the orange molly quickly ate. I am stupefied as to why the black molly died, and now one of our red finned sharks is floating strangely now and then. Please help, I don't want to lose all of our fish!!!

Answer
Hi Brittany,
I know you said you tested your water. But what you described all points towards a pollution problem.

*Did you make sure your ammonia and nitrites were definitely ZERO and your nitrates were under 20?

Your tank may not be cycled completely. It may have occasional ammonia spikes every now and then or maybe even traces of nitrites.

As for the greenish little eggs the molly produced. Those were simply unhatched babies. It can be a sign of stress if a livebearer releases such undeveloped fry.

I would immediately change 30-50% of your tank water for now. Always make sure to treat the new water with a water conditioner and make sure the temp is equal to or just a bit warmer than your tank.

This is the best thing I can recommend for your fish now.

Best of luck and I hope all goes well!
Karen~