I know most if not all tangs like to graze algae on rocks/walls etc but a 40 would really be too small IMO
. I have a similar issue w/ my 55. Just hair algae on the back wall. Very little if none on the LR
. I was going to get a lawnmower blenny but I'm interested in something more colorful too.
One of the main things that I have been trying to do is get to the bottom of the issue in the first place instead of just trying to "put a bandaid on a broken elbow"
How are your parameters? Do you have a TDS
meter? You use RODI