because they are good algae eaters and very interesting fish.
"Almost" a
must have in planted aquariums. ;op

Not true at all. A Pl*co is an excellent algae eater and very
interesting fish. A Chinese algae eater is only a good algae eater
while it is very young. The adults are moody, agressive and eat almost
no algae at all (note that I mentioned the horrible state the aquarium
was in when I obtained it - algae was **everywhere** and this thing
wasn't even touching it). Plus they're ugly as all get out. Pl*co's or
snails are both excellent alternatives - some people that keep planted
aquariums hate snails but I've never had a problem with the ramshorn
variety I keep eating any of my plants, they always stick to the algae.
And of course the Pl*co is a foolproof cure for algae.

-Daniel