I've only had mine for a couple of months, so I can't really comment on the growth rate. I can tell you that they are very efficient algae eaters. I have a 120g Malawi tank that has about 300 lbs of rock. It had developed a significant amount of brown algae on the top surfaces of all the rocks when I introduced the BN (female about 2.5"). The algae was completely gone 48 hours later and there's been no sign of it since.