My flowerhorn is around 3 inches long and iv just put up a similar thread regarding what I should be feeding and how much, how often.
As a result from the replies iv gotten from members here im feeding hikari gold medium cichlid pellets 3 times a day for a week and then changing to New Life Spectrum sinking cichlid pellets 3 times a day for the following week and then back to hikari and so on... This is to give him a variety.
I also feed a frozen bloodworm cube twice a week and frozen market prawns around twice a week. This again gives him a variety of food and all he needs in his diet
Maybe you could try something similar with yours. If your flowerhorn is too small to take the medium size hikari pellets you can also buy the same thing but in "small" so they easier for him/her to eat