I've heard Discus are very hard to keep, but people who keep them say it's not as hard as people say. Could I keep 1 or 2 with a red-tailed shark, 3 clown loaches, 2 cory cats, and 1 clown pl*co? I am just worried about the clown pl*co sucking on the side of the Discus. Any suggestions? Also, could I use RO water straight for them?