Once you get better lighting your algae is going to bloom so you might want to hold off on getting rid of the snails or else you might be out buying more again
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The ammonia cycle appears to be nearly over so it should be alright to leave them in there. I am assuming of course that the .25 ammonia is test kit error seeing as how there are no nitrites or nitrates.
As far as feeding the snails that you have, I have noticed my snails appreciate a bit of Nori now and then so you could try supplementing their diet with that until the algae starts to take over