ok, so i got a new tak last thursday, i had it set up on thursday and let it run overnight. On friday i got a heaterand put it in. On saturday i got 3 X Ray tetras and 3 eon tetras. One neon died on the way home and I found one dead the next day. On sunday i git 3 glass bloodfin tetras and 3 bala sharks. yesterday i got 2 lemon tetras and 3 neon tetras to replace the ones that died. They were all ok this morning but when i got home from school both the lemons and the lone neon from the forst batch were dead. One of the balas in floating around on his back but hes alive. Ive had a hard time keeping the temp stable and last night it dropped to about 72, but i dont that would kill them ina day. Any explaations?