Wow, that is some crazy filtration you all are talking about. I have a 240 (8x2x2) with only 1 fx6 on it. I also have a 60 gpd drip system on it. All the trays are loaded with biomedia. The only sponge filters are the ones around the outside of the trays. Stock is 2 18" retics, 1 9" retic, 2 14" hystrix, 1 14" clown knife, 2 poly senegalus, and 1 5" electric blue acara. I do have a DIY k1 2 liter bottle filter, and a sponge filter rated for 100 gallon tank, but I do not think they help much. Anyway long story short, I keep 0ppm ammonia, 0ppm nitrites, and usually 50 to 80 ppm nitrates. So in reality other than some higher than I would like nitrates, my parameters seems to be fine. I have run this like this for 3 years now without any major incidents. I am going to start growing pothos in the water though to help with the nitrates. It worked great for my discus tank. I had them started in my 240, but got red hooks (which are now gone) and they ate every last bit of my pothos. lol
Sorry about the rant. lol
Now for the actual question, I just went through the exact same problem. I had my male retic get parasites somehow. I treated with Prazi 1 time for 6 days with the drip system off and that seemed to cure my little boy. He is eating like a pig now. I was prepared to inject Prazipro straight into the rays food though so they would ingest it, but I got lucky and did not have to do that. I am not sure where the parasite came from, could be the frozen shrimp or the frozen bloodworms or even the live earthworms I feed. I only buy non wild frozen raw shrimp, but I feel that is still where they came from. We are not cooking it for our rays to make sure everything is dead in the shrimp. Long story short the rays are now fine and eating like little pigs again.
