The problem only concerns the C. trilineatus, paleatus, aeneus, leucomelas, and sodalis individuals and one recently-added B. splendens.
Recently, I have been treating them with Rid-Ich + once I noticed them scraping. I stopped treating them about a week ago. I had treated them for a few days and a few more after the symptoms disappeared (Sorry, I don't keep specific records of dates and such...). After the last dose, I had performed, over a few days, water changes. One at 50%, the other two or three at 25%. After each water change, I had also supplemented the water with the appropriate amounts of aquarium salt, Stress Coat +, and Stress Zyme. I just added two new fish yesterday, and they're perfectly fine (Which isn't surprising since the two new ones and one veteran resident are Loricariids....).
All 5 have been scraping themselves each and everytime after I so much as put my hand in the tank to siphon detritus, perform a water change, stir up the sand bed, etc... They also breathe relatively fast (2 cycles per second). These symptoms present themselves for about 10 to 15 minutes, then abate.
What in the world am I supposed to do? If they're scraping, doesn't that mean they're more susceptible to disease? If I do nothing, it's obvious what will happen. Either way, I'd likely lose the fish and they'd lose their lives.
This is getting to be extremely frustrating. They'll go for a month of health, and then it's right back to death and suffering. If all these 6 cats die, I'll just get an Erpetoichthys calabaricus to keep my plecostomids and banjo cats company. They are supposed to be hardier than these corys and brochi, and do well in most community tanks.
What should I do?
