Ill start with my set up. 10 gallon tank, at about 75 degrees, lots of cover with large castle, 3 fake plants, 2 live plants, and air input. 4 females, 4 males, two snails, and one beta, yes I said Beta lol I have purchased everything, but the snails, at Petsmart. The first "phase" of my aquarium I lost all my females and had to replace them and lost my beta. I thought that I had too many males and they were picking on the rest, including the beta that had severe damage on its tail and fin. Now that I have replaced my beta and females, they are doing great and now I am losing males like crazy. The beta IS NOT attacking my fish. None of the guppies have damage what so ever they are just dieing. I also have a filter system, so along with the live plants I am pretty confident of the water quality....but that is the only thing I can think is the issue. Any ideas?????? ***Side note, one male died literally within hrs and others have died about a week after being put in the aquarium.