NOPOX works well but I still have algae

[Hythe]

My 500Litre tank had severe green hair algae(GHA) and I started to use NOPOX around six months ago. It is a excellent product and from having GHA covering every rock surface plu rear tank glass, using NOPOX reduced the algae by 90-95%.
My question is HOW do I get the algae to go completely?
After the inital reduction of GHA - which took about three months - I did reduce the dose of NOPOX. But because the GHA was not eradicated I had to increase the dose back up to 10ml morning and 10ml in the evening. That's 4ml per 100L daily. That seems like a lot. What do you think about the dose rate? If I increase the dose what could go wrong? Tank Parameters are: NO3 zero. PO4 0.08. CA 490. MG 1450. KH 8.1dKH(2.9Mql) PH 8.0. SP=1025 (Using Redsea Pro)
My skimate is the colour of assam tea (using Redsea C skim 1800) and it pulls about 500ml out daily.

[Reefing Madness]

How many Turbo Snails do you have in there? They keep mine at bay, they snarf it down pretty good. Another way is to get rid of the rest of your Phosphates. What water are you using? RO/DI? What are you feeding that has phosphates in it? How often do you feed?

[Hythe]

How many Turbo Snails do you have in there? They keep mine at bay, they snarf it down pretty good. Another way is to get rid of the rest of your Phosphates. What water are you using? RO/DI? What are you feeding that has phosphates in it? How often do you feed?

Thanks Reefing Madness. I have no Turbos, I think the ones I had got eaten by the crabs. Do you have crabs in your tank?
Yes our water is RO/DI + redsea plus salt.
I feed mysis and calanoid shrimplets. A bit like cyclopeeze. I feed once daily and then some more cyclops after dark for the corals.

[Reefing Madness]

Try and cut your feedings to every other day. I dn't have any crabs in my tank, my Pink Tail Trigger would just eat them. Try Turbos, and or Sea Hairs. They'll mow that little you have right down.