I have a 75 gallon with 6 discus and 3 clown loaches and a bristlenose pec. The loaches hide in one of the hollowed out fake diftwood peices that everyone seems to have from PetSmart. They only come out in the morning to create havac for the first feed of the day.
I've always liked clown loaches but these guys are getting pretty big, I never see them except for the 5 minutes of havoc in the morning. I'm thinking about taking to the lfs but concerned that won't do well there.
I'm of the opionion to not put clown loaches with discus. I can't imagine how large a pack of 6 would get in a 150 gallon over time. I don't think your discus will miss them.