Good afternoon and thank you for trying to help... I have a tank with 4 happy seahorses in it. There's a purple firefish in the tank that loves to eat whatever the seahorses miss. Anyways he rubs the front of his body against the substrate constantly throughout the day so I though flukes or some type of parasite. I got some prazipro and dosed the whole tank since there's no possible way to catch this firefish. Believe me I've tried everything possible. He's just too fast and has too many places to dart. I dosed the tank and followed the directions closely. The directions say to replace 75% of the water 7 days in and redose. I just redosed which probably brought the PPM of the prazipro very high. I let it go another 5 days with the two doses so now we were at 13 days. I dosed one more time, and this is when I put two and two together that I had likely raised the level of prazipro to a extremely high level since I didn't do the water change. So on the 15th day I turned the skimmer and carbon filters back on because the seahorses were hardly eating and not active any longer. So the prazipro was finally getting to them. BTW I only ran the biological filter during the 15 days. Another side note, there's 4 pistol shrimp living in the tank and 3 peppermint shrimp. Part of the clean up crew if you will. Interestingly the pistol shrimp and seahorses interact all the time. I've watched closely and the pistol shrimp will not disturb the seahorses even if the seahorses scares it when going for food. I didn't want to catch any heat for keeping them together. Also have a talespot blenny and Rainford's goby to clean up algae and food. Seahorses run the tank though. So long story short, I though I had treated the firefish with the 15 days of prazipro. Unfortunately he's still rubbing the front of his body like gills and belly against the sand. So clearly has something going on. Please help. What should I do next... I'm afraid he has parasites still and the last thing I want is them to spread to the other fish or worse the seahorses. The seahorses and other fish do occasionally eat pieces of there dinner that have fallen on the substrate where the firefish has likely poo'd. It's my understanding that is how most parasites pass to new hosts. And lastly I really really don't want to put the seahorses back thru 2 weeks of treatment again. They lost they're appetite and would hardly move around after I would dose the tank. Any help would be greatly appreciated. I'm running out of options and don't understand how the parasite survived those 15 days. Or am I just completely off and maybe he doesn't have a parasite..... Truly appreciate you reading my post and thanks in advance for the help!