Internal Parasites?

[DBam]

Hi, never really had this problem before and I don't want to rush out and buy anything that won't work or will harm my other fish. A couple of my newer additions have failed to put on any weight/size, and there's been some stringy white feces showing up in the tank. I've been diligent about increasing the volume of w/c's, increased the temp by a couple degrees, and made sure there's been lots of food available. Still no sign of improvement in these two. Affected fish are cichlids, and the only other tankmates are other cichlids and a large black ghost knife. I have an empty 20 gal I could move fish into for treatment.

What kind of parasites am I dealing with, and what is the best way to treat it?

[jobber604]

What type of cichlids? angelfish? discus? geophagus? oscars?

[DBam]

Satanoperca. The other unaffected cichlid is an angel.