Though i don't have Flower Horn i have a great interest on that fish. One of my friend is a FLowerhorn specialist. I gathered these details when i had a chat with him.
Due the big size they can reach, Flowerhorn need big aquarium with a lot of free space for swimming; a 200 litres tank is the minimum you can offer to an adult fish to let it live healthily. It is a really strong fish and can live in different water conditions without having problems, anyway it is important to provide a temperature between 25°C and 30°C;
pH value is also important, because acid water can tone down fish colours and make it sick, the ideal condition is a light alkaline water, with a PH between 7 and 8. Moreover it is necessary to avoid sudden condition changes of temperature and chemical values, because they can make Flowerhorn being more sensible to sickness like bacteria attacks.
A larger aquarium will also reduce the amount of aggressive behaviour if your fish does behave like. You can keep your Flower horn alone in the aquarium, but it is not obligatory as long as the aquarium is large enough to house other species of roughly the same size and temperament. Large cichlids from South America that will not tolerate being bullied by the Flower horn is one example of suitable tank mates. Since the Flower horn is a territorial species you should fill the aquarium with decorations that create natural borders. If the fish can keep out of each others way and stay inside their own territory, the amount of aggressive behaviour will decrease. Keep in mind that some Flower horns like to destroy plants.
Choose pellets of a suitable size as a basic Flowerhorn food. Flowerhorn cichlid can be kept on a diet consisting only of pellets but will be healthier and will breed easier on a more varied diet. Pellets are a good base but you should complement that with other food types such as frozen food, shrimp, crabs and crayfish, fish meat and other meaty food types. Never feed you Flowerhorn cichlid pork as it is to fat to be a suitable Flowerhorn food.
Suitable Flowerhorn fry food is during the first few days newly hatched
brine shrimp. The fry can there after be trained to eat crushed pellets and flake food.
Flowerhorn cichlids are not picky eaters so don’t be afraid to use your imagination while deciding what to feed them. And oh yeah, a bit of common sense is good to ,-)