This is some crazy growth of ciliate sponge which is a poriferan sponge. Not seeing coral amongst them, I would remove rock and place in a container of tank water and scrape off with the edge of a knife and pull stubborn ones with a dental pick or small crochet needle. Exposing them to air will also knock them downI just started up this tank again with old live rock and sand from 18 years ago. I did clean the sand prior to putting in the tank. I use instantocean salt, RODI water. Thee has been nothing live put in the tank yet. I can see some kind of Alge growing, but don’t have a clue where it came from of what it is. Any ideas? I was hoping to start adding livestock soon. Temp is steady at 26degC salinity is 30ppt.
Thanks for the quick reply. Crazy interesting as there is nothing but 18 year old sand and rock. Not sure where it could have come from unless something can be dormant for long periods, or came in in the instant ocean. I will do as you have described. Thanks.
