I adore my SAE! I don't know if it is male or female and do not know how to tell the difference. It doesn't matter, though. I love this fish to pieces. I bought it when it was about 6 or 8 cm long, and put it in my planted tank. He mowed down my hair algae that I had, and keeps the plants algae free better than the otocinclus who live in there, too. Soon, I will have to either get a much larger tank for it, or trade it in for a smaller one. I cannot recommend these pretty fish enough! They are really nice, will eat algae and flake, and other foods, and get along with everyone.
Very aggressive feeders, otherwise friendly to other fish. They will destroy Myriophyllum sp. (Parrots Feather, Frill, etc.). If I had to do it over again, I'd put the SAE as the only fish in an aquatic garden. The more regularly they are fed, the less interested they are in algae.
I owned a SAE for about a year. One of my mother's coworkers was trying to get rid of him, so I volunteered to give him a home in my 140 liter tank. He immediately helped to rid me of my algae problem. He was a very active fish and loved to pick on the others in the tank. Unlike plecos, he didn't get lazy and quit eating after he grew quite long. Sadly though, he passed on some time ago. I have since kept Plecos and Otos, but none have been near as fun as the SAE.
My Siamese Algae Eater is very rude. He's so hardy. Unfortunately, he outranked my Plecostomus and Chinese Algae Eater, so they died. The Chinese Algae Eater even got a bite from the SAE.
At one point, Crossocheilus siamensis was an Epalzeorhynchos species. However, recent reclassification of the species has placed it into a separate genus. As for Milton's comment, C. siamensis does have a tendency to be aggressive, or at least domineering. As a result, they do not work well with their own kind and other fish that may have the same niche.
I bought 2 SAE's but unfortunately one didn't survive the 3 hour trip home. The survivor however seems totally happy "schooling" with 5 Oto's in the tank!