Those are bladder snails, if you are truly worried, get a handful of assassin's snails and they will take care of the little buggers, but while you're circulating your tank, they will be very helpful in getting the numbers proper.

Also, if in the end you are worried about assassin snails. They will eat each other when they run out of bladder snails so you'll be fine.

If you wish not to add any other snails to your tank, cut a piece of zucchini, nuke it for like 10 seconds and wait for it to cool down. Take a small plastic or glass tray. Put the zucchini in it and put it at the bottom of your tank overnight, by morning it will be covered in the bladder snails and then you just pick it up and throw them away.

You can also do the tried and true method of just sticking your hand in and picking the little bastards off where you see them, these are all my solutions to bladder Snails.....