Yup it's green hair algea you will have to manuly remove as much as posible. Are your hermit crabs a good size I have a few different sizes of herhimt crabs the red leged ones seem to eat more algea than the blue leged ones I don't know why but they do a good job. I also got rock from different places so I would get a few different critters on it. One rock in particular had a bunch of mini brisle starfish on it they do a good job of eating algea also. I have bristel stars in almost all of my rocks now. turn your lights off for a couple of days and when you start useing them again start with
1-2 hour time period perfurably itinics only
2 -2hour time periods with 2-3 hours inbetween first period with itinics only second with white light only.
3- 2 hour periods with 2 hours in between first period with itinics only second with white light only and the last 2 hrs with itinics only.
After a couple of weeks then you can change the lighting a bit 3-2-3 hour periods with hours in between first 2hour period with itinics for 1hour then white light only second with white light only for first hour and the add itinic and the last 2 hrs with white light only and the last hour itinics only

you are still trying to similate the natural light shifts but shortining the time of light exposure. I found this worked for me I have kept me lighting down a bit and there seems to have been no negitive aspects so far. I now leave the itinics on longer in the evening, the corals seem to love it itinics are closer to their natural light spectrum 6500 luminums/h as that is what is it a the equartor. why we use 10k and 12k I don't realy know except to get more penitration. Everyone forgets alot of these corals come for depths alot deeper than our tanks. So to get the penitration use a few more bulbs and use 6.5k daylight bulds and run an itinic which will help drive the light deeper in the tank algea will grow better also. Just a thought.

Bill