Heres a picture of mine. I've been battling them for at least 6 months. This is only one day after completely siphoning them out. They completely disappear at night and are back during the day. I've tried everything I've read to try, short of the UV. I just purchased an 18w emperor aquatics to run on my 57g. Hopefully have it online this weekend. I don't have a positive ID on them but it definitely killed all my snails. Hermits and emerald crabs seem to be fine though.
Steps I've tried
1. 3 day blackout (this cleared the tank for about a day. I noticed small patches by that night and by the next day it was business as usual for them.
2. Dino X ( this worked incredibly well, completely rid my tank for a week, and then all hell broke loose and they came back stronger than ever) increasing dosage had no effect.
3. Hydrogen peroxide 1-2ml per gallon has had no effect.
So my plan of attack this round is going to be the UV, blackout and Dino X.
