I don't think they are THAT hard to grow out.
You just have to be very diligent with your tank, and have it set up right.
1) Temps around 80
2) Lots of airation. If you think you have enough, add some more. I run a big rena 400 air pump pushing two sponge filters and a HOB filter on my 30 gallon grow out tank. The high temps required will lower the water oxygen level, and cause a Hait to stress/bloat/die unless you compensate with more airation.
3) Good food not high in protein with some fiber, and do not overfeed. I like NLS thera +a. I also let algae grow on my grow out tank so they have some greens to eat/graze on. This will also help to keep bloat away.
4) Good clean water. However, for younger Haits, I'd do lower percentage water changes more frequently instead of one big water change per week. Better yet if you can set up a continuous drip system. Seems like the less you mess with their tank, the less they stress/bloat/die. Keep the nitrates 0 if possible. I let a lot of algae grow on my tank that scrubs the nitrates. The algae also gives them some greenery to eat, and seems to help with bloating as well.
5) Put the tank in a low stress/traffic area when growing out. The less people stomping by the tank the lower the stress on the fish, and they'll have a lesser propensity to stress/bloat/die.
6) Don't buy a whole bunch of them, keep them in the same tank, and expect them all to live. They can be hard on one another, and even the tough and genetically great ones can stress/bloat/die from this stress.
7) It's often been said that if you try to house a big tough Hait with another big tough fish (ex midas or trimac), they'll both die. The Hait will kill the $#!+ out of the other fish, and then will stress/bloat/die. I highly recommend keeping them alone or in a pair.
