I have a 10 gallon tank and am fairly new at this hobby . I recently purchased 4 guppies this past week an i already lost 3. Lost the first 2 days after i got them, then second about 4 days after that, an today coming up on the one week mark i lost my 3rd. My fourth guppy that is still alive is a male, idk whats wrong but he keeps stayin in the corners of the tank and then moves violently toward the bottom of the tank and then straight back to the top. I saw this in my first guppy that i lost that one a female though, then 2nd guppy jus hung out in the coners until i saw him settle in the bottom of the tank an when i woke up he was dead, an last night my 3rd loss which was a fat female jus slumped around the bottom of the tank and when i came home 2day from school it was dead in the back corner of the tank. Please help me idk whats wrong with my fish, i have 0 ammonia in the tank an i have a ph of 7.2ish pleae help me i dont wanna lose this guy if its not 2 late . Also in the tank i have 4 hatchets an 2 neon tetras, an one small pleco. they have been in the tank since i first purchased it and they all are healthy, one hatchet caught "popeye" but he's over that now an are all healthy, aside from my one guppy that remains. PLEASE HELP