i bought a 3 gallon starter fish tank. i had already had a gold fish that i won from the fair so i decided to get it a tank with some friends. i bought 4 other gold fish, a sucker (bottom feeder) fish, a black moor, and a tiny small little crab. i followed the instructions, i cleaned the tank, ran the water over the pebbles to clean them, poured tap water into the tank and waited till it was 68-74 degrees, fed them, but after just 2 hours in the tank, the black moor and 1 gold fish died. im scared that when i wake up in morning, they will all be dead. what did i do wrong? were they just bad fish from walmart? does walmart have a return policy on the fish?