They can grow to 6" but I buy them here at about 1.25 inches, I buy 2 or 3 of them even for 20 inch tanks, and move them as they get too big for the tank. As juveniles they aren't as good at eating algae as they are when they get older, so I get several. I feed blanched zucchini 2 or 3 times per week to aid their diet needs, which enhances growth and appetite. As they age they get very good at consuming red beard, and hair algae. When they get larger they often get rough with congeners and at this point I would move one out. I have a standing offer to friends and planted tank people I know, that when their algae eater gets too big I'll take it from them. I keep the larger ones in larger tanks, and if the tank is big enough they seem to be able to live well together in numbers again, as they did when they were young. Returning them to your LFS is also an option. But, as your community of SAE aficionados grows, someone with larger tanks will surely be in my position and realize their full value. Also be sure you are getting the correct species: Apparently, here in North America, were aren't getting Crossocheilus siamensis any more, were are getting C. langei, C. altrilimes, and infrequently C. oblongus and C. citripinnis. And as luck would have it, the most common available here is C. langei, which is also a very good consumer of these kinds of algae. On the other hand C. altrilimes doesn't, and seems to like to eat Java moss and other soft tissue plants. They are also fairly aggressive with C. langei in my experience. So, be careful when you buy them. But, there is nothing equal to their ability to consume these types of algae, and I would not even consider a planted tank without these guys. They are that good!
