ok this stuff is starting to reall spread and im getting worried and i need to know if i need to destroy it

or it its like some sort of benificial algae
its slimy but it doesn't rub right off the rocks

these are all on different rocks anyone help plz?
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My 55g Chronical of addiction...
Mistakes Have been made in the past.....still trying to clean up from them in the present....mistakes will be made in the future.....so what do we do?......

we party until we make another mistake!!!!
WARNING: Corals in Tank, Add Crabs at own risk