i just bought a red pacu last week i have it in a 55 gallon tank. the 1st day i got him he was fine yesterday he was laying sideways on the botton but he would move if scared. the guy at the fish store told me that the water needed to be about 78.. i had the wated at 70. oned i got to water temp up he started acting ok. i also have some guppies in the tank. the guy told me the fish would eat them. i don't have any rocks or sand in the tank. what all do i need???? please help.