i use Malaysian trumpet snails in all of my sand tanks. they really help keep anaerobic pockets from forming. most people don't like them cuz they do multiply like crazy, but i like them for their cleaning and sifting abilities as well as being a nice snack for my clown loaches. win/win as far as i'm concerned.
i never went soil bottom on my planted tanks, thought for the next one i definitely will. that's why i would put a mesh barrier down, to help keep the plants rooted and to keep a cap on the soil as my tank has clown loaches, blue zaire fronts and geophagus altifrons who all love to sift and dig. would be a mess if they got to the soil and muddied up the tank.