can we add snails to aquarium? what does they do and are they friendly

hi! jusk like any force, snail can be used for good and for evil. they have a reputation of rapidly devouring plants, multiplying like crazy and turning aquarium into an unsightly mass of creeping grey slime, but his only the dark side of the snails. when properly managed, snails can actually do a lot of good in your aquarium. if you introduce factors that balance thier numbers, they will settle in thier designated ecological niche in your aquarium and carry out the same beneficial work that they do on the wild...oh by the way the another problem with snail in aquarium is, because they are scavenger they eat eggs of fish..hope this help..

Perhaps this is not a good idea. The snails grow so fast and they grow more and more. They eat the weeds which they are very nice decoration for your aquarium. The fish need the plants, such as the weeds. It makes them healthy.

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Snails are good if you have a puffer fish or a tiger fish to balance the eco system in your tank. Actually, snails can mess up your aquarium by eating plants and making your aquarium dirty, they also can reproduce rapidly and make your tank unsightly just like what Bart said

There are several kinds of aquarium snails and most of them do not eat healthy plants but rather will eat dead and dying plants. The trumpet snails act like earthworms in that they will burrow into the gravel and eat uneaten food and by doing so will aerate the gravel keeping it from becoming anaerobic. The reason the most snails reproduce so fast is because there is plenty of uneaten food (most probably overfeed their tanks) but if the snails do not have much food they will not reproduce as fast. In one of my tanks that I purposely overfed so that the trumpet snails would overproduce, I put in some "killer snails", These snails are attractive and hopefully will control the number of trumpet snails that I have in that tank.
Unless you have a very large (75 gallon or larger) I would not get a common pleco because they get up to 2 foot long. If yo are getting algae and need a fish to get rid of it then the bushymouth, clown or rubber lips plecos. These plecos do not get very large (maybe u to 7 inches for the largest species) and do eat algae. If you have plenty of true aquatic plants growing healthy in your tank then you may not get algae. The hight plants will utilize the nourishments in the water that the algae need but you must make sure that yo are giving the higher plants the light that they need to grow.

yes you can they harmless unless your fish is dead they would eat on decaing matter. they will clean your aquarium and eat the agae on it.