Well so far my Lapradei has been the slowest growing of all the polys i've owned. Picked him up last winter and hasn't grown much, maybe 1". He eats like crazy but just doesn't grow.
That all depends on diet tank size tank mates and water quality. I had one that shot up fast from 4-12 inches but in the past year hasn't grown too much part 15. When they get bigger their growth rates slow considerabley
Sent from my DROID RAZR using MonsterAquariaNetwork App