have a 75 gallon cichild tank. for about a year i have about 15 fish of various size, and types in the tank. i am new to this, and i am learning as i go. i know i have made some "mistakes" with some things, but i was wondering what is a safe amount of fish to have in a tank of this size. i have around 20 or rocks making plenty spaces and caves for them to hide in. i also have a fruval 405 for my filtration. if there's any other info i could get a read to make this a better tank for my fish i would appreciate any help.