Hello all. Been a while since I posted anything, been busy with life and such. Looking for some advice. 6 months ago I had a beautiful guppy breeding tank (75 gal) with a few neon tetras and Kulie loaches. Guppies were breeding like crazy and had a really nice tank. Unfortunately something is in my water that takes out my guppies after a few months. Have all the water testing kits, hit tank numerous times with antibiotics, etc. it just isn't working. As it is only my guppies that are dying, guppy are just not for me. Have a doz Rosie barbs, and few platies that are all doing good after about year (other tank, same care). Thinking about switching over to a swordtail/platies breeding tank. Have a few questions, put this tread in the beginners section as assume fairly basic questions and may be helpful to some starting a similar project. Questions are: 1) Breeding rate, assume going to less than my guppies. What to know what I am getting into to purchase the correct amount of breeding stock. 2) Can Swordtails and Platies interbreed? If yes is this a bad thing? Looking for a tank that will self repopulate. 3) Have a fairly heavy planted tank, expecting only a small percentage of the fry to make it to adult hood (not doing breeding nets, etc.). How long does it take a swordtail to reach maturity. My guppies seamed like were breeding after just a few months, full grown in about 6 months. 4) See swords/plates ranging from colors of green/black, red/black, and yellow's. Will these guys interbreed or do you need to stick with one color. My guppies could care less! Little more info on my tank. When things were going well, was getting tons of fry. Other fish in the tank got so used to them they stopped eating them all togather. Was great, they just die out faster than can repopulate. Tank is 75 gal, heavy planted, 20% weekly water changes, 5 tps of Florish weekly, tried putting a little extra salt in the water (maybe tps/5 gals) on water changes, didn't seam to make much of a change so stopped after a few weeks. Well water, high Iron content. Been keeping fish off and on over the past 40 years. This past year only really got serious (actually did water changes, going with live plants, getting a water testing kit and using it). Oh ya, low tech tank, no Co or high light levels (2 watts per gallon). Plants are Amazon swords, Water sprites, couple of other more hearty plants can't recall names and a bunch of java moss. Just looking for a little guidance before starting my new breeder tank. Thank you in advance for your input.