Hi-Hat rubbing sides (glancing) on substrate

[hornetmaker]

I have a 120g salt tank that has been up and running about 3 months. I have one Hi-Hat that is about 4 inches long. I have noticed him rubbing on the substrate occasionally as he swims. I was wondering if this is normal or not.

 

[snorvich]

I have a 120g salt tank that has been up and running about 3 months. I have one Hi-Hat that is about 4 inches long. I have noticed him rubbing on the substrate occasionally as he swims. I was wondering if this is normal or not.

It is called "flashing" and is probably symptomatic of a parasite, most likely cryptocaryon irritans (ich).