reverse osmosis -deionized. if you are going to stay in this hobby, you should buy your own R.O.D.I unit and make your own water. it's cheaper and you can be sure it's quality.
this should work for you-
Aquarium Water | Reverse Osmosis | RODI Water | ReefKeeper Water | Mighty Mite 50GPD with DI Added
well, if it's long, green, hair-like strands, it's either hair algae or bryopsis. bryopsis can be eradicated by raising the magnesium levels with kent tech-m. i have seen this first hand. it can't be any magnesium additive- it must be the kent product.
i only had to raise my mag level to 1600 and it withered away.
some snails take a while to acclimate. they will get moving soon, but don't get excited if they don't eat the hair algae.