These fish are a member of the carp family but are unusual in as much as they are solely vegetarians. As a carp they grow quite quickly and large, eventually reaching several feet in length under good conditions. They need plenty of space like Koi carp because they get very frustrated in cramped conditions and will jump vigorously.
In America grass carp are widely grown as a food fish in the same way we grow trout. The Farmers who rear them actually cut the grass of the fields and scatter the grass cuttings on the water to feed them although they will take commercial fish food as well. Grass Carp are prodigious feeders and have been used in the Everglades experimentally to clear the vegetation that threatens to block the waterways. In many states of America however they are considered a pest stripping rivers of all their vegetation so they have been banned.
Some Grass Carp are imported into this country for sale in the aquatic trade but they are not to be recommended in a well-planted pond for they will strip it bare as they get bigger. Grass Carp are rather plain being the colour of an ordinary carp, but an albino form is sometimes available which is yellow in colour. This will show up in the pool very well, but large specimens are horrendously expensive to buy and even small ones cost many pounds each.