Those 2.5" clown loaches will soon become food for the aro. Your rtg will reach 12"+ in about a year and the clown loach will be only 3"+. Clown loach grow very slow.
from person exp n from seeing others tanks, aros even when a lot bigger tend not to bother clown loaches... just make sure u keep the loaches in a small group.. say atleast 3