Algae on back panel of tank.. Clean it or leave it. The three sides of my tank are clean just back has algae on it ive seen tanks with dirty "natural" looking back panels.
Very nice tank. What you are getting is from cycling the tank. I would leave it till it cycles. The back will get covered with Caroline algae once it starts to grow
I would remove it. Not for anything chemical or for the health of the tank, but instead just aesthetics.
At first I thought like lots of people. The back in coralline would be more "natural". What I realized now is it just makes the tank look small. Having a blue or black back helps give an illusion of depth.