flowerhorn gender/growth rate

[reptiletom]

I have a 5" flowerhorn that is about 1yr old. This fish was about 1" when I bought him/her. I keep this fish alone in a 20gal tank without substrate. I do frequent water changes to keep water parameters good (temp≈ 80°, pH ≈6.8, nitrates under 5ppm) and feed a mixed diet of flakes, hikari carnivore wafers, frozen prawn, and occasionally live crickets. Everything im doing seems to be ok but the fish is still very small for his/her age. I eventually want to upgrade to a larger aquarium but the fish is still small and it doesn't seem necessary yet. Am I missing something here? I read in several sources that the black markings on the dorsal fin could indicate that the fish is female .. is that why she's on the smaller side?

[coolingeffect]

i would venture to say that the reason the growth is slowing down is because the fish is starting to stunt. A 20 isn't a very big tank and really 5" isn't all that small. Im sure others will chime in, but that's my initial thought.