Hi,
Bristlenose plecs are brilliant algae eaters but if it is for your 13.8 gallon tank they get too big. A couple of otocinclus would do the trick and they only grow a couple of inches.
I personally would take both of the snails out and put them in a seperate container for a few days wihout food and they should clean each other, my apple snails are always crawling over each other and don't have algae on them. Maybe put them in an icecream tub floating in the main tank so the temp stays the same.
Emma