I 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.