Dealing with dust algae

[604reefer]

Hi all,

I'm dealing with a dust algae issue that seems to be getting worse or at least steadily bad. This is just 2 days of buildup. The door in the background and windows surrounding do not let any sunlight hit the tank.



This spot I let build up a bit to see, looks pretty brown.


I've been googling and there seems to be no consistent advice to deal with this. The suggestions I've read range from lights out for 3 days straight to letting it grow for 3 weeks then remove with a big WC.

I'm only 4 months in on this tank, 1st SW tank. It's a 20g, "wild wild west" tank - no sump, no refugium. I have a hydor slim skim nano and eheim 350 surface skimmer.

Inverts:
- 14 snails (mix of cerith/astrea/margarita)
- fire shrimp
- rarely seen emerald crab
- 9 hermits

I do a 20-25% WC weekly. Temp is 77F, 8.3 PH, and always 1.025sg. I've cut back on feeding to 1x per day from 2-3x when I noticed last week nitrates were around 20ppm.

My coral (euphyllia/discosomas) and fish all look happy except for the torch with a mood that seems to change like I change my underwear. This could be because it was splitting from 1 skeleton to what is definitely 2 and maybe 3rd coming.

Do I just need to clean every other day and wait it out or is this not "new tank syndrome"? Should I consider that I've overstocked this 20g with my 4 fish (clown x2, chromis, blenny) and crew?

Thanks for the help.