Try an ATS to eliminate hair algae in the display. By growing algae under ideal conditions in an ATS it will out compete the algae in the display. You can build an ATS very inexpensively. I built a 3 sheet one for less than $30. They take about 2 weeks to start growing but work really well. I have a DIY thread on building them for under $30.Believe me, if I could get rid of the hair algae I would. But he’s got plenty of places to hold. I also don’t do emerald crabs... once I had some try ‘n tear up my zoas. Not getting them again lol.
Hope that didn’t sound rude it kinda did but I didn’t mean it to XD