I have gone through 4 guppies in the past month and I cannot figure out what is wrong with my tank because my cories, neon tetras, and placo have been around for the past 7 months. My temp is about 75F, my ammonia 0, GH 30, KH 80-120, pH 7-7.5, NO2 and NO3 at 0. I am also adding stress coat as a water conditioner. I have been adding aglaefix due to some huge algea problems, but from what I've read, if algae is growing readily, your tank is probably in good health. OH! and I do water changes every 2 to 3 weeks and have live plants. I cannot figure out what is wrong with the setup. Does anybody have any ideas?