What else will slow down algae?

[Rogue951]

Current parameters
PH - 8-8.2
Ammonia - 0
Nitrate - 0
Nitrate - 0
Phosphate - 0 maybe trace. can't tell with this damn color card.
Calcum - 700+

2x 250 watt 10K phoenix halides on for about 8 hours.
actinics on for around 12-14.

I have noticed that the algae I have (I think I got hair, turf, bryopsis, bubble and red bubble) the green ones are turning light green in patches and fading. but some patches are still going strong.
Manual removal is really hard because it's so dug into the rock, the rock is actually coming apart.
I have chaeto in a fuge, and an army of margarita and cerith snails. Any other snail I find dies way too quickly.
Oh and a small urchin in there.

I have a crocea clam, a bunch of Smal SPS', 2 large hammer colonies, a lot of xenia and a gbta.

what's the minimum amount of light I can give them?