I have a 1/4 acre pond with submerged trees and pallets for spawning structures. I intentionally purchased rosie reds because I knew how deadly there are when it comes to bass and crappie fishing. Yes fatheads will spawn roughly 4 times a summer, april,may,june and september. They will stop spawning when the water hits around 80 degs and will resume one more time in September. The fish will stop spawning when they run out of room. Your idea sounds fine, except that you are missing 1 major factor zooplankton and phytoplankton. Since you have built this indoors without thought of a natural food source you will have to feed them. Also your biofilter is too small to properly clean the approx 2,500 gallons of water. 1 female fathead will produce between 80 and 300 offspring/spawn. You willl run out of room after the first spawn and the fatheads will starve. I predict your project will fail. You just do not have sufficient room or food to succeed. This not what you want to hear,I know, but quickly you will realize what I am telling you is true.