Try lowering the light, take some foil and place up in the hood to deflect it away from the front of tank, also, try 8 hours of light per day, and perhaps use only 1 bulb, not both.
This alga and it's bloom/persistence has nothing to do with Ca or Mg
As stated, for many, it went away on its own. So a little correlation can account for such reports that also have nothing to do with it's "cure".
I did nothing to the Mg/Ca in 2 tanks, it went away in 2-3 weeks.
I did a just the CO2 a little and waited.
A client's tank, simply reduced the high light to low light, all algae issues went away.
Others have also simply allowed it to go 3 weeks or so, then resist the temptation to wipe, and then a few days later, they wipe and clean real good, siphon it, correct light/CO2 issues.
My Ca and Mg levels have been all over and I was easily able to get under control. My KH's where 12 down to 1.
Ca from 2ppm to 70ppm, Mg from .5 to 50ppm.........
Big donkey ranges I'd reckon.........no issues.
I took samples from other tanks, could not induce it in others that had the same water, nutrient dosing etc.
The only differences that where of note: light and CO2.
Of course if you have only 1 tank and do not investigate inducing it, then there's really not much you can say, other than there was correlation.
Excess light "causes algae", I think is a much more realistic view
But none of these folks seem to wanna talk about that, go figure.
Algae are not limited by nutrients or CO2, so what are they really limited by?
Plants? Often are limited by CO2/nutrients, so ...........
And when the plants do well, the algae does not, this is universal.
So the goal and focus is plants, not algae. I've said this for 15 or more years now.
It really has not changed.