Ok so i have about a 30 gallon tank it has two filters both with the filter that has all the stuff you need... well i have one zebra danio (his other friend disappeared over xmas vacation (friend was feeding them)) two black skirt tetras and 10 gold fish of two different types. Last night i bought two albino corey cats and two sucker fish! I let them float for about two hours and released them.... went to bed about 3 am and got up and at 10 am they were dead...... I have no clue whats wrong... I had the water tested and they said its good..... i have 6 decorations all of the rock type..... i had an air thing that goes ont he bottom too.... I took it out to put in the other tank... Please Help I have no clue wahts wrong.... Maybe too many gold fish giving off too much ammonia???? Although i had the water tested and it was fine... IDK PLEASE HELP! Thanks in advance! Mrs. Caldwell!