Why no more Coraline?

[hkgar]

My tank has been up for about 5 years and I have always Coraline growth. I have needed to scrape from the corners weekly. Now I get none and only a hard green algae growth in the corners where the mag cleaner has a hard ttime getting to. Why no more Coraline growth. I want it back
Water Parameters
CA 420
Alk 8.0 dKh
PH 8.4
Phos 0
Nitrate 2
I run a phosphate remover 24/7 and a skimmer about 3-4 days per week. Tank is a 90 Gallon with 500 watts of MH (10000K) and 260 watts of PC Actinic.
I ran 14000 K for about 9 months but just switched to 10000K 2 days ago. I switched to hope to get better sps growth.
Gary

 

[hkgar]

About 6 weeks ago I noticed that my CA had gotten up to over 600. I have finally gotten it reduced to it's current level but while it was high I continued to had high amounts of Randy's alk mix to try to get the alk level in balance with the CA. I was raising the dKh to close to 20 or more.

 

[sean48183]

Probably something to do with this imbalance. Once it fades it takes a minute for it to come back. With your levels where they are it should come back shortly. Run your actinics longer as corraline seems to really like this light. I ran my actinics only for about a week a couple years ago to get rid of my algae growth and the coralline went nuts.