Question about polyp extension

[togor]

Hi guys, all my acros are usually with all the polyps out during the day. During the night, they've a bigger extension to catch food. However, one friend has all the acros with incredible polyp extension day and night.

I use Zeovit method (he also uses it partially). Question is: what can I add to increase polyp extension in acroporas? feed something specific, reduce water movement?

 

[togor]

My current params are: Ca:420, KH:7,5: Mg:1400

Reef volume :300l main tank+sump

Water movement: Tunze 6045 + Tunze 6055 + return pump Eheim 3000

There is not any fish that disturb/damage the acros..

Any ideas?