hard to say from that pic. may be Dino, use a pipette , take some sample , stirr in one cup, if she reform in few min. may be Dino, Scope will be the best to see, anyway.
STOP change the water.
Reduce light up to 5 hrs.
Reduce food.
Increase flow, use more Active Carbon.
Increase , slow the PH , use kallkawasser.
Use 100 micron sock , change every day.
Blow rocks.
Using refuge , full of Chaetto will help.
some ppl use Coral snow after blow the rocks.
High PH is welcome, very slow.
Stop adding any Amino acid or dif. stuff.
Monitor the snails, if wont move or die remove it.
Connect the IN take air of Protein Skimmer from OUT side.
DO NOT PANIC.