I think the fact that you have a few issues going on in the system right now is part of the reason the coraline isn't growing. High PO4
and trace low alk
and high lighting all contribute.
With the Hair algae I would concern myself more with correcting that right now then work towards the coraline. By reducing the amount of excess nutrients in your system you will see a decline in the hair algae and this could also help out in the coraline growth. As others have suggested adding GFO
will help reduce the PO4
. I would also suggest frequent PWC
of 20% or better. (what kind of salt mix are you using?)
I think I suggested pruning your refugium also. By doing this you will remove some of the nutrients that are stored in the macro, also it promotes growth and will help remove more nutrients from your system.
I would also reduce the lighting period per day for a little while until you get the hair algae undre control. The best method of control is manual remove coupled with the other suggestions mentioned. I think by getting a handle on the hair algae and the source of it's fuel you'll see a turn around with your coraline growth.