Yellow clown goby scratching against hammer coral

Hi I've had this clown goby in my tank for about a month now in my 20 gallon long reef. He's been doing great and sitting on my hammer coral almost all day. However today I've caught him scratching his side against the mouth of one of the hammers heads. Could it be ich? All other fish are fine. Parameters ph 8.3, ammonia 0, nitrate 0-5, nitrite 0, temp 77. Anyone have any ideas? I can have a quarentine ready. Thanks.