my teacher used to be a ornamental breeder he said use a 3 foot tank, feed them a high protein diet even though they r mainly herbivores give them worm etc , and he said he kept only one pair in the tank, and kept them in low light with floating margarine lids on the top :/ sounds stupid but he is a aquaculture teacher. plus u dont want the silver dollars to be to big mine are about 7 inches long and past breeding maturity. good luck