What kind of snails do I have and do they need to mate?

Okay, I just got two little snails for my fish aquarium. I read about a type of snail called an Apple water snail. Is that what kind these are? They are about the size of a pea and they are brown. I want them to multiply and eat the algae and stuff in my tank. I had this kind once before and they multiply like nuts. But do they need to mate or do they reproduce asexually? I only have two and i have no clue how to tell if they are male or female so if this kind needs to mate to reproduce then I might need some more. Help? Please?
Answers:
Not all snails are asexual, if they are apple snails then they are either male or female. Here is a site that will teach you all about them an even if they are another type they will tell you that too. http://www.applesnail.net/

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First off, from where I am I can't tell what species of snail you have. All snails(that I am aware of) are EXTREMELY small when they are young. All snails are male and Female. As long as you have two snails they can breed because technically they are male and female! Strange isn't it.

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Dont' know anything about snails, sorry. Maybe you can ask a pet store or get a library book on the different types or search the web.

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Snails are asexual and can reproduce on their own. But, I've been told that they are most likely to do so if there are multiple snails in the tank.

I had 5 snails at one point and none of them reproduced. Other people told me that they had only 1 and it reproduced like crazy and then they had way too many.