For some reason I always have guppies die in my community tank...I can't figure it out. To clear things up, its a 30 gal, penguin 350 biowheel filter, all levels are good, 80 degrees F. Tankmates are two Angelfish (~2-3 inches each), and two opaline gouramis. The guppy's seem to do well for 2-3 months, then die inexplicably. This has happened with cheap pet store guppies, LFS guppies, and even ones I've grown from fry in a smaller tank. The angels and gourami's have been in there for about 2 years now too. I'm wondering if the angels are too aggressive? If that is the case, why would it take so long for them to die then? I have a lot of plants and driftwood in there for cover, and really want a tank that has a thriving little ecosystem of fish from fry to adult. Would going with mollies be a better choice since they are bigger? Any suggestions appreciated.