Dinos. May not be the toxic version.
Dino's are usually long and stringy (snot like)with an air bubble at the end. Additional info will help with your issue.
Last week, as a final battle against problem GHA, I removed every rock and scrubbed the algae off. The rocks were then sprayed with Hydrogen Peroxide, let stand 4-5 minutes salt water rinse and return. One third of rock each day over 3 days.
Might be a cause of whatever this is?
It is possible you wiped out a good portion of beneficial bacteria and caused another cycle have you tested ammonia and nitrite ?
Alk/mg/cal do you run reactors? carbon or gfo.' wc history. do you over feed ? Ther are toxic and and non toxic Dino's snails will die after eating the toxic kind.
It is possible you wiped out a good portion of beneficial bacteria and caused another cycle have you tested ammonia and nitrite ?