nice invert that will eat algae and not get eaten

get olive nerite snails specifically. they aren't easy to find, though, and you may need to special order them from your LFS.

most snails won't eat aquarium plants as long as they are well fed, though some may eat plants not matter what, such as giant apple snails.
 
Olive nerite snails are the way to go...they are about 1" full grown and won't eat your plants. Mine keep my plant leaves and glass spotless. Plus they have a trap door and can retreat into their shell if the tiger barbs decide to attack.

I ordered mine from Wilma ($2 per snail and very healthy):
http://www.jayscustomcomputers.com/wilma/
 
Nope, and they can't breed in freshwater. If you get males and females, they will lay eggs, but the eggs won't hatch (from what I gather they only hatch in brackish water).
 
Olive Nerites are indeed plant safe, and you can get some here: http://www.rainbowsnails.com/ Also, one variety of Apple Snail, Pomacea Brisgesii are plant safe. They reproduce sexually, so you have to have a male and female to get eggs, which are lain above the water line, so population control is very simple - just remove the clutch and throw it away. Other larger varieties, such as Pomacea Paludosa and Haustrum will eat plants very quickly. Planorbids, or "ramshorns" are plant safe. They only get to about the size of a pencil eraser, reproduce hermaphroditically, and lay eggs underwater, so it's easy to get too many. Giant Columbian Ramshorns eat plants and Asolene Spixi a.k.a. Zebra Apple Snail will eat tender plants. I have them all.
 
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