From what I understand, this isn't the case with Siamese Algae Eaters,
crossocheilus siamensis. It
is the case however with the Chinese Algae Eater,
gyrinocheilus aymonieri (usually but sometimes they're actually
gyrinocheilus kaznakovi).
Note that there are also many species that are sold as "Siamese Algae Eaters" but in fact they are NOT
crossocheilus siamensis. Look for a zig-zag pattern on the edges of the black horizontal stripe down the fish's center, and that the stripe extends all the way to the fork of the tail. At rest
crossocheilus siamensis will sit on its fins.
As to the differing species, there is the False Siamese Algae Eater,
epalzeorhynchus sp. (some believe it to actually be the Siamese Stone Lapper,
garra taeniata), which also does not prefer algae. They have smooth edges on their black stripes and they do
not extend through the tail. There is also the Flying Fox,
epalzeorhynchus kalopterus (not to be confused with the Siamese Flying Fox, which is another common name for the true
crossocheilus siamensis Siamese Algae Eater). These have smooth edges on their black stripes and very dark tops, sometimes almost looking like another stripe. Another species is
crossocheilus oblongus which is closely related to the true
SAE and is also usually found schooling with them in the wild, but this also has a smooth edge on the black stripe and it doesn't extend into the tail, and again, doesn't prefer algae as its main diet.
If your
SAE looks like this it's the real deal:
If it looks like one of these, it's not a true algae eating
crossocheilus siamensis Siamese Algae Eater:
I credit this information and the pics to a link I don't have anymore.
