Yes, I would switch to high heat if that's a better treatment for the scaleless fish.
I'm not sure. It just says "API Super Ick Cure contains an ingredient, Malachite green, which causes discoloration in the aquarium water" but I threw out the box already.
I've used it before on scaled fish to good success. But ive had to half the dose because of the scaleless fish.
Either treatment will work ime but both carry risks. Probably known but some thoughts:-
Heat speeds up the cycle and the white spot doesn’t reproduce at 86F (as long as no cold spots in tank) but that often means it gets worse before it gets better (and extra water flow is needed to aerate water for lower O2 / damaged gills). Secondary bacterial infections more possible. So imo need to catch it early for this method.
MG will work (perhaps a little slower by itself) with the usual risk these meds are trying to kill the parasite before the fish and they readily get soaked up by organics / carbon. Deactivates very quickly. If fish survive first few days seem to be ok with it so half-dosing to start anyways could be useful. Then slightly higher dosing to more normal dosing - watching for rapid gill movement (panting).
Or as V suggested, swap to a different med (med options more limited at shop over here).
I have done both together over summer but it was a shock to them. Cottonmouth struck shortly after so that wasn’t a fun summer.
Problem is treating once on fish as many cures are then ineffective (ie have to wait until cyst bursts and it becomes free-swimming in water).
Salt will work but more suggested for colder-water fish like goldfish.
Triple sulpha or metronidazole will also work, albeit slowly and will kill it off where on fish.
Here, I’d continue on with present method (equally you could swap to heat method) and would add triple sulpha (either method).
I had one or two spots survive at high heat and meds for over a week so can be persistent when trying to treat for sure.
