Started my first 10gal 6 months ago. Cycled then added 3 guppies. They were fine for a few weeks, then 1 died. I waited a couple weeks and the remaining gups were fine, so I added 3 more, 2 zebra danios & a sucker cat. A couple weeks later lost 2 more guppies, so again I waited 2 weeks, then replaced them and added 2 black skirt tetras & a Cory. Within a month all the guppies were dead, but everyone else was doing great. I gave up on them and haven't lost a fish since, but I'd still like to know why I had such trouble. The only visible problem was that their tails got a little tattered, one almost completely gone. I never saw anyone picking on them though. I've heard they're overbred and weak. Any thoughts?