I have 20 fish in my 29 gallon and the nitrates go up in little as a week without a water change, so be careful with 22 fish Luckily I have 3 tiger barbs that are doing fine, with 5 neon tetras, 3 cobra guppies, 5 guaraníes: 1 pearl, 1 blue, 1 pink kissing, 1 powder blue, and 1 red flame. I...