Okay, I am about to purchase another aquarium because I would like to have Discus. I would like some info about whether they can be kept with large angels; also the temperature, PH and so on, that the Discus require. someone told me years ago, that Discus are hard to keep. I know they are quite expensive. If I get a 30 gallon aquarium, how many Discus and Angels (sclarare) can I keep?