Maroon substrate that disappears at night

Dub · Jul 23, 2020

Hope this is the right forum. I have a 34 gal display with 9 gal. sump. All parameters are in line and stable. Life stock include 10 fish, a few LPS , a few SPS and a clean up crew. The display is 8 months old with 15-20 lbs live rock, 10 lbs live sand, enoys 120 scimmer and 4 lb bio block. Lighting is AI Prime 16 HD that runs Saxby light program at about 70% capacity for eight hours plus ambient room lighting.
Each day the sand will be covered with a dark maroon film that will disappear each night only to return the next morning with no action on my part. This film covers about 70-80% of the substrate and seldom gets on the rock.

Reeffraff · Jul 23, 2020

Sounds like cyanobacteria to me based on the color you describe. Check NO3 and PO4 levels with a high quality test kit and make sure you have enough flow in the tank.

anth · Jul 23, 2020

Could also be dinos. They disappear into the water when there is no light then reappear when lights come on as they are photosynthetic

Reeffraff · Jul 23, 2020

anth said:
Could also be dinos.

While the nightly disappearing act is a common trait for benthic dinoflagellates, cyanobacteria can exhibit this behavior as well. I think the key tell here is that dinos are not dark maroon in color and thus the OP is unlikely to be dealing dinos in this case.

Dub · Jul 23, 2020

Thanks guys. Guess it is cyano, now to look up the solutions. Again thanks

anth · Jul 23, 2020

Reeffraff said:
While the nightly disappearing act is a common trait for benthic dinoflagellates, cyanobacteria can exhibit this behavior as well. I think the key tell here is that dinos are not dark maroon in color and thus the OP is unlikely to be dealing dinos in this case.

Ahh sorry, missed the maroon part.