I have a 90 gallon DT with 12 fish totaling 35 inches. Most are on the smaller size and under 4". If I am going to go fallow in my main tank, and I also need to do a copper treatment for ich, what sized QT/HT will I need for those 12 fish to make it manageable? I currently have access to a 50 gallon tank, is it possible to make this work with biofilter? Or should I just wait until I can afford a bigger tank?