Help diagnose my clownfish

[prior20]

I have looked at images of common clownfish diseases but I can't find what this is. At first it looked like a growth on his gill and now (picture) it seems that the growth has come off and it looks like a chunk is taken out of the gill. He is in a quarantine tank and is now not eating and seems to be getting worse by the day.

 

[hollister]

He looks unhappay. What size tank ? And whats used for water flow?

 

[prior20]

My display is a 60g cube with 2 mp10s and the quarantine is a 30 with a koralia 750. I bought him and another picasso about a year ago and they have been the healthiest and hardiest fish I have had. This came out of nowhere.