I have a 110 gal fish only tank right now. I have a porcupine puffer, a maroon clown, and a cuban hogfish. All seem healthy. I do 10% water changes every 5 - 7 days even though I only have 3 fish. I only use RODI water. My question is can ick just appear even though I havent added any fish? Only my puffer seems to have it on his fins. It really doesnt look exactly like ick however. Ick looks like little grains of salt. These seem much smaller and more "flat". Is is ick? Should I treat for ick? Can it be something else?