Good luck with him
I had mine at just over an inch in length at the end of july... this year. He is now a chunky 6 inches (well just over). He eats like a pig... gets fed 3 times a day 6 days a week on prawns, frozen fish, bloodworm, shrimp and worms. His main diet is hikari gold cichlid pellets and new life spectrum cichlid pellets. I do 40-50% weekly water changes and gravel vac on his tank, which is 120 gallons.
I do have good filtration. 2 external tetra ex1200's and an internal fluval 4 plus giving me 3400lph turnover which drops to around 2700lph with filter media.
As i mentioned in previous posts, iv tried adding other fish with him when he was smaller at around 4-5 inches, like a 6 inch jack dempsey, a 7 inch buttikoferi and even a 10 inch plec but all failed. He killed the jd and butti within 24 hours of them being in the tank and he stressed the hell out of the plec so i had to rehome it. I tried taking the fh out and rescaping the tank to calm the aggression but nothing worked. He is going to have to stay in the tank alone. Which is ok with me as it means no other fish can be harmed.
If you can get that 125 gal for him that will be ideal for life. Its kind of a shame that they cant be housed with other fish even in 100 gal+ but at the same time its awesome to see how they behave in the right environment
Good luck and keep us posted with updates. You will soon see a dramatic difference in size. Just be sure to feed 2-3 times a day on a high protien diet as flowerhorns have a very fast metabolism. They can and will eat more than oscars and grow quicker
This is mine around 3-4 weeks after i got him...
Il get a pic tomorrow of him now so you can see the difference in the 5 months iv had him...