VERY IMPORTANT WHAT TANK DO I GET thanks?

haha ok. well you need at least a 150 gallon tank. personally i would drop the catfish and get a 100 gallon tank, or you could ditch the koi. i would ditch both because they both get really big and get angelfish, scissortails, danios, gouramis and other tetras but thats your decision. you should cycle a tank this big for a couple months.