Flowerhorn not eating

[RD.]

And the reason is because your fish metabolism will run much faster, therefore you feed it more, and in result it lead your fish to end its life quicker than usual.

The same rule applies to all fish, and certainly all FH, no matter what the strain is. "Pump em up bro" comes at a cost. Not a problem with young fish that generally have higher metabolic rates, but not so good for mature fish once their metabolisms naturally slow down with age.