Apistogramma Agassizii Double RedFish Size Guide: The 'Maximum Size' outlined below is the length this fish can reach as a full grown adult. For the actual size please use the select menu above. Discus. ae prefers younger stock for their better ability to adapt to new water parameters and higher tolerance against transport. On rare occasions you may receive larger specimens when small fish are unavailable, however the smallest should be expected unless the size is noted as "Large" or