There's nuisance snails that are little and brown that can be carried in on a plant (you should have some plants by the way) and then there's the big snails that they sell in stores. I'm pretty sure apple snails are the name. They help keep it clean. By the way if you get any nuisance snails then clown loaches will snap them right up. For a FW you pretty much need to keep up with water changes and when you do then siphon the water from the very bottom with a vacuum so that the crap in between the gravel is taken out of the tank. What size is your tank?
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55gal,260 watt PC(2x65 actinic,2x65 10k daylight,8 lunar LED) 45#LR, 45#LS, 3 maxi-jet 900's on a natural wavemaker timer,phosban reactor, 5 gal fuge (built out of standard 10 gallon tank) with chaeto, grape, and feather caulerpa, sealife systems protein skimmer, wet/dry, 4 blue/green chromi, 1 skunk cleaner shrimp, 1 coral beauty,1 true perc, 5 mexican turbo snails, assorted dwarf blue leg hermits, astrea snails, and nerite snails | 
FW Cleaning Crew? 
