My original group of 2" juvies and subsequent grow-outs from breeding, of which I raised a bunch, consistently reached 5 to 6 inches first year, females a little smaller, then another inch or so in year two.
I won't try to parse out all the variables of why this or that species grows slow for some and well for others, too many variables and it's not always something you can put your finger on. But here was my routine-- Food: Omega One color pellets and Omega One shrimp pellets and NLS, including Thera-A, occasional freeze dried treats. Note: Omega One cheapened their formula a little while back, I don't use it anymore. Feeding: once or twice a day, depending on their size, my mood, etc. Water: pH mid-upper 7s, GH and KH moderate, low nitrates, temperature high 70s. Water changes: once a week, 50-90%, sometimes depending on how clear my well water is that day.
It's similar with all my fish and has been for years, except exact chemistry or temperature can vary between tanks, or exact version of NLS might vary for some species. Nothing special or heroic-- quality foods, no soy or excessive starch/grain ingredients, regular though not obsessive water changes, reasonable chemistry and temps, don't overfeed as it's counter-productive, decent sized tanks from day one.
