Not a hybrid. . . it is an Acarichthys Heckelii, if you don't want to take my word for it, post it up on the SA section. Acarichthys Heckelii have only been spawned in captivity a few times as far as I know, they have very special requirements and it is VERY unlikely to hybridize because of the breeding strategy that they use. With regards to the yellow. . . wait till he/she hits maturity, yours is still a juvie. Also, the tiny mouth of a Discus is no match for a Heckelii's mouth, Discus may be waspy, but, they can't back it up!