Not all plecos are compatible with discus. I've heard some plecos will attach on the side of discus and suck on their slime. Young discus(2-4") should be kept in a barebottom tank and fed several times a day and a water change of 20-50% daily is ideal. If you want to add substrate go with adult size discus if you have the money for it. Carbon should not be added to the filter if you have discus, rumor has it that carbon may cause hole in the head disease. If you wanna learn more about discus, register for this discus forum: http://discusasahobby.com/forum/index.php