well im totally clueless as too what happened in my tank of BGK's in the tank i had a few outher fish i got a pair of angel fish and i had added my male mollys and sword tails so my females could be alone a bit about 2 weeks ago neway about 3 days ago my male swordtail bit the dust didn't think anything of it the next day I had put the female molly that just gave birth i have been doing this for the last 7 months there just there long enof so the baby can grow a little and get stronger at swiming once all the female;s give birth i wait 4 days and put them all toghter again in there live bearer tank neway the female i put in there was dead bye the end of the day all my tests where comeing out perfect right where i wanted them. the next morning i woke up tested it and my nirtrate went from 0 too the highest on the test i just tested the night before. then i did a 50% water change as soon as i saw that my water chages are done with spring water totally pure verry soft what my BGK's love neway then i came home after the day out and they were all dead every last one off my fish in that tank i already miss my betta =p i am clueless anyone got any ideas and how can i prevent this happening again