For that size tank are you sure you want tank mates? If so not to many. Maybe some corys and a school of rummie noses tetras. Qt any dither fish before adding to your main tank. Qt for a month. So if just starting qt your new discus in the main tank and your dither fish in a different tank. Just seems many dither fish come to you sick. Last thing you want to do is add sick fish to your main tank. Next where are you getting your discus from?