Bright green slime

[dement]

My aquarium is 250 l (about 67 us gal.) with few lps and soft corals, 3 blue green chromis, 3 nemos, 4 damsels, 1 zebrasoma scopas, and 2 lysmatas.
About 3 weeks ago green slime appeared on sand surface in my aquarium.
Now it spreading on almost all sand and partialy on rockwork too.

There were no setup changes for several month, I do regular water changes and also regulary I change GPO. Now I do increased water flow.

Can you give me some advice how to defeat that green slime?
I do not want to use chemical remover, I'd like to find out what is the source of my problem.

Thanks for info.

[mcgyvr]

Probably green cyanobacteria..
A picture (turn blue channel of light off or way down) would help confirm

Siphon as much as you can out with your next water change then turn lights completely off for 3 days (longer if you dont have corals)...repeat as needed every few weeks till gone

[dement]

Thanks for quick answer.
I do forgot to add photo, so now I'm addding.
Why do you think the blue light reduction will help?

[dement]

Sorry, I just read your answer again..you told me to switch off blue light for photo making.
Now it makes sense

[IowaReefer]

Green cyano. Reduce feeding, eliminate broadcast feeding, and do a couple water changes and should clear up in a few weeks. Vacuuming helps too. I wouldn't worry about turning your lights off unless the problem persists after trying the aforementioned steps.

Forgot to add, check your TDS and replace filters if needed.