I agree with Colin that only one species of loach should be in any tank, and given the size of the tank and the species mentioned here, the Clown is not going to work; Clown loaches need at least five and this requires an 8-foot long tank. Return it to the store ASAP. Without a group it is going to have serious problems.
Second point though, is that Corydoras and loaches should never be combined. The loaches are all more aggressive feeders, and cories will lose out. The two fish have very different temperaments.
Second point though, is that Corydoras and loaches should never be combined. The loaches are all more aggressive feeders, and cories will lose out. The two fish have very different temperaments.