Yea thats bad looking. Im guessing the high levels of nitrate are helping this. 3 steps to help get this started.
Make sure lights are on for a max of 8 hours a day and cover the nearby window to the left of your tank. We need to control the lighting so the algea cant grow as much.
Remove fish and corals and place in bucket A with tank water. Remove rocks and place in bucket B with tank water and scrub all that junk off there and rinse em good. Also clean inside of tank including sifting the sand to remove algea growth.
Drain your tank down to 20% then add 10 to 20% and remove back down to 20%. Do this a few times to make sure all that nitrate is gone then fill her back up and put everything back.
It is very important that your filter is not touched, looses water or anything to mess with it. While the above steps will solve your tanks algea and nitrate issues it will also fully destroy your biofilter inside the tank leaving only you normal filter left to handle your nitrogen cycle. You should buy and use or take a water sample to you LFS
every 3 days for the first 12 days or so to make sure your not getting any chemical spikes that will harm your fish.