you don't need a tall tank to get a good size Kok on a Flowerhorn....you can get a good size one in any kind of tank but if you go with tall you leaving out the lenght and width for your flowerhorn to grow much larger than what you can achieve from a tall tank like a hex....you can gain a large Kok from those specially formulated pellets to grow the Kok size to a really large one....and its all depending on genes and how well graded it is and how the quality is in the tank....tall tanks doesn't mean bigger Kok