hi so i brought a 11 gallon tub for a Quarantine tank. then i brought like 100 feeder guppy and put it in the tub. i added a air stone a bag of circled filter media on top of the air stone and a heater. i added api general care, api em erythromycin, and itch x. i waited 1 week and only 3-4 dead ones so i changed out the water and dose the meds again. few days later i saw all of them is dead. what did i did wrong? did the meds kill all the bacteria from the circled media?