I don’t know for sure what initially caused the turf algae. My nitrates have always run around 20 ppm. My tank is 1 year old. I was trying to improve coral growth by broadcast feeding coral food. Reef roids, AB+, phyto, reef chilli etc and i fed the fish 4 cubes of various frozen food a day. My phosphates got high and my DOS for the soda ash stopped for a few days and the alkalinity dropped. I assume that was the initial cause Of the turf algae. Since then I have stopped broadcast feeding of the coral food other than a periodic target feeding and have cut the fish food in half. I ran GFO for a while but it is now off due to the vibrant. My phosphates are 0 and my nitrates continue to be 20 ppm. I have a good octopus skimmer and a decent clean up crew. Sea Hares are hard to find. If I locate one I will purchase it.