i found this at
http://aquaticconcepts.thekrib.com/Articles/Plant_Pests.htm
Algae Eaters
The most effective control of algae in a planted aquaria is via algae eating fish. It is especially critical in the set up of a new tank to make sure algae does not get established before the plants have had a chance to establish themselves. For this reason and to help the biological filtration get established, it is recommended that some hardy algae eaters are added right away.
Black mollies Black sailfin mollies are excellent candidates for the break-in period of a planted tank since they are cheap and easy to find. They are usually considered expendable and are removed after a month or so. It is important to not feed them. If they are fed, they will not be quite so eager to consume alage. When they are hungry, they are eager consumers of most algae types seen during the break-in period.
Otocinclus sp. Otocinclus are diligent algae eaters, but are best kept in schools due to their small size. One per 10 gallons is a useful rule of thumb. Various species of otos are seen in the shops at various times; most are good algae eaters but some seem to prefer the slime coat on fish to algae. Unfortunately, there seems to be no way to distinguish the "attack otos" from normal otos.
Otos seem to be very delicate fish, but this is probably due to capture and shipping abuse rather than an inherent weakness. When a fish shop gets some in, it is wise to wait a while before purchasing to account for die offs. Most people report getting a dozen and having them die over a period of a few months until just a couple are left. Those then seem to last for a long time.
"Plecostomus" sp. Plecostomus is the generic name for a wide range of sucker-mouth fish. Only the smaller types are useful in a planted tank, since the larger varieties tend to eat the plant right along with the algae. Two common types that are useful are the "bristle-nose plecostomus" and the "clown plecostomus" or Pekoltia. Both stay under 4" long and don't seem to cause too much plant damage. Sometimes broad-leafed plants like Amazon swords will be scraped a little too closely by the plecos, so they bear watching.
Their diet can be supplemented by blanched zucchini and bottom feeder tablets. They also appreciate a chunk of driftwood in the aquarium to satisfy their need for cellulose.
Siamese Algae Eater The Siamese Algae Eater, Crossocheilus siamensis, is a very good algae eater and is known to eat black brush (red) algae. The only problem is that these fish are hard to find. There are two common fish in this family. The most commonly seen is Epalzeorhynchus kallopterus, commonly known as the Flying Fox. The Flying Fox is the more attractive of the two. It tends to have a brownish body with a very distinct, sharpedged black stripe with a distinct, thin gold or bronze stripe above it. These tend to be very aggressive when they are full grown and don't eat red algae (as far as one aquarium reference is concerned).
The other member is the Siamese Algae Eater. It is the same shape as the Flying Fox but tends toward a silverish body with a somewhat ragged black stripe. There may be an indistinct gold or bronze stripe above the black. These are definitely not aggressive; they are good companions for discus and small tetras.
When they are young, the differences between E. kallopterus and C. siamensis may not be very apparent, especially if you haven't seen both types together. Unfortunately, most wholesalers don't sell fish to stores by their scientific name and the common names that are used some- times get pretty silly (like "siamese flying fox"). If you really can't tell which one the store has, buy it anyway, but be prepared to sacrifice it if it turns out to be the wrong kind (unless your fish aren't bothered by it, of course).
Farlowella sp. Farlowella are useful algae eaters although they are very sensitive to water conditions. They type known as the Royal Farlowella will get too large for a plant tank and may cause damage.
Snails are usually considered disasters in a plant tank, but with dense planting and good plant growing conditions, the right type of snail can be very useful by consuming dead plant material and detritus. Any damage they do cause will be compensated for by fast plant growth.
Malaysian trumpet snail The Malaysian snail, Melanoides tubercularia, is an interesting creature in that it lives in the substrate during the day and only comes out at night. Its shell is a perfect cone shape and gets to about 2 cm long. It is a livebearing snail and reproduces quite readily. It is considered beneficial to a plant tank and doesn't seen to harm plants, even in large populations. They are hard to find for sale, but usually come for free on plant shipments. If desired, Clown Loaches will keep them and other snails well under control.
Ramshorn snail Ramshorn snails are very common and come in various sizes. Their shape is as their name suggests. The smaller varieties (under 1 cm) are not too damaging to a plant tank, although they seem to relish the tender leaves of the Hygrophila family.
The other type is the dark and light brown striped Columbian Ramshorn that can grow big as large as 2 inches in diameter. The stripes run the length of the shell with a pattern of random width light-dark-light stripes that stays constant throughout the snails life. These snails are *extremely* prolific and have a terrific appetite for plants.
Pond snail Pond snails are football shaped snails under 2 cm in length. They are to be avoided, as they will happily eat all your plants.
Mystery (Apple) snail One of the most beautiful kinds of snails are the Mystery snails. These snails have a shape similiar to the Pond snail, but their spiral is rounder, and they grow much larger. They can reach tennis-ball size if well taken care of. The come in many varieties. The snail's body can be dark, or almost albino (very light with a bright orange speckle pattern). The shell can be dark, bright orange, albino, or multi-colored striped (length-wise like the Ramshorn). The Apple snail variety typically has the multi-colored stripes, with a dark body. In general these snails don't eat living plants. They prefer algae and dead plant/animal material (canned spinach will get you a very large Mystery snail).
Snail Prophylactics To guard against unwanted snails, use a weak potassium permanganate solution. The Manual of Fish Health recommends a concentration of 10 mg/l as a 10-minute bath as a general disenfectant for aquarium plants. Then rinse them in running water. This kills snail eggs and parasites and might guard against algae spores.