Cyano?

[JDubb_4051]

Tank is 5 months old...thought I went through this already but it’s been hanging around for a few weeks. Have done a few large-ish water changes each weekend (about 12%) on top of my AWC which is doing about 25% month. Nitrates at 2 and phosphate at .08. RO/DI water.

Don’t want to treat with chemicals yet if I can avoid.

Have reduced light cycle to 8 hours. Flow hasn't changed. Goes away some (at night). Have siphoned my sand...it comes back. Very little on my rock...that which is there blows off easily

 

[LuizW13]

Looks pretty cyano-ish to me. There should be guidance for dealing with it somewhere in the forum- i'm sure you can find it pretty easily with the search feature, it seems to be a fairly common thing.

 

[LesPoissons]

its cyno. Increase your flow at a lower level. get your phos down. decrease light intensity and decrease length to 6 hours. Gravel vac.
What creatures are in your tank?
Otherwise its still going through the uglies and you can use chemiclean or something for cybo/red slime.