Maybe you heard that if you breed a platinum and regular brown bichir, then all of their babies will all look normal brown, but they will have the hidden recessive platinum gene in them. So if you breed those normal looking but hidden platinum gene babies back to the platinum parent, then half the babies will look normal and half will be platinum. Then if you breed those platinum babies to each other or to the original platinum parent, then 100% of the babies will be platinum. The platinum gene in fish is definitely classed as recessive, and that's what animal breeders do to get a recessive gene trait that they want to keep and breed, if they are starting with only one specimen of an animal with the recessive gene they want.