Help with GSA

[nijat11]

1. 800 liters 180smx80smx55sm
2. 6 months
3. Sump; 6500 liter return pump
4. WRGB. 14:00-22:00 (W:80%, B:80%, R:80%, G:50%) 22:00-23:00 (WBR:15%)
5. ADA Amazonia V2 and fine gravel
6. . During the day pH drops from 7.5 to 6.2. Drop checker get lime green.
7. Tropica Specialized every day 20ml and Tropica Premium every day 20 ml (going to change to EI from this week)
8. Every 7-10 days 50%
9. Multiple cryptocorynes, multiple echnidoruses, multiple buchephalandras, Rotala Roundofolia, Rotala Orange Juice, Rotala Wallichni, Alternathera reckini mini, Alternather Cardinals, Golden Nesaea, Ludwiga Super Red, limnophila hippuridoides, multiple anubiases, Java ferns, Java moss.
10. Lime Green During the day.
11. Angelfish - 12; Rummy Nose Tetra - 30; Kardinal Tetra - 12; Black Neon Tetra - 10; Corrydoras Sterbai - 10; Corrydoras Panda -10; Apistograma Ramizeri -4; Apistograma Columbian -2; Apistogramma cacatuoides-2; Ancistrus -4; L333 - 2; L340-1; Nerite Snails - 10.
12. Please see the attached full tank image.

I have a problem with green spot algae (GSA), they keep appearing on my alternatheras, crypts, java ferns, even on echinodoruses.
Will appreciate your advises.
Thank you in advance.

 

[hypnogogia]

Have you tried reducing your photo period?

 

[John q]

Photo intensity is more troublesome than period, maybe reduce that. Also adding extra phosphate helps. Maybe target 4ppm.

 

[nijat11]

Photo intensity is more troublesome than period, maybe reduce that. Also adding extra phosphate helps. Maybe target 4ppm.

What will you suggest? 70% ? I keep on 80% because my tank is 80sm long.

 

[John q]

What will you suggest? 70% ?

You could try dropping WBR to 70% to see if it helps. Obviously there's a balancing act to be had between providing enough light for plant A and to much light for plant B, trial and error is what's needed.