Read up on marine ich. In a nutshell, the parasites had burrowed under the skin and feeding off the fish tissues. See that you have corals in tank. Catch it out and use copper treatment in QT.
Where to buy those really thin and small squarish magnetic cleaner? Saw some posts is 'little two fish' the only one? Any other magnetic cleaner that you are using and would recommend?
I recently added a gonio and did some reading up on replacement. Most articles recommended on sandbed but a few said can be on rocks mid way of tank. Need good lighting and not too strong flow. Sharing my 0.000002 cents worth
Depends on what the particles are. If detritus then filtering and skimmer will usually remove them. Bt if they are pods they may continue to reproduce. So finding the cause of the particles will enable you to find the best solution.