Ugly phase. Is this Cyano?

[BruceOnTheCoast]

Hello Reefers!

I have a 75 gallon tank that first filled on October 5. My current parameters are:

Salinity 1.23
Nitrate 4.4
Phosphate 0 (Hanna Low range)
Alkalinity 9.32
Nitrite 0
Ammonia 0

I have notice alkalinity rising, and nitrate dropping, have never got a reading above zero on phosphate.
Tank has 5 assorted small fish, some Zoa's, and a Duncan, all of which seem fat and healthy. Shortly after tank was cycled and 2 clowns added, went through a brown diatom phase, added snails and it went away. Now I have this black/charcoal colored matt all over sand. If it was reddish I would say its cyano, but the black color is throwing me off. I have vacuumed it out but it came back hard, been there about three weeks. Also seems to me entirely on sand, not rock.
The tank is one that I had to take down about 5 years ago, when i set it back up I used about half new dryrock, and the rest is old live rock from before, which had set dry for several years and then cleaned before new setup.
If its Cyano, I have dealt with it before and there are plenty of resources and advise here to control, but could it be something else?
Thanks,
Bruce

 

[dwest]

Looks like cyano to me.

 

[Tahoe61]

That's cyanobacteria.
At that point I would use some Chemiclean and then address the cause.
Check you N/P values, lighting duration and intensity and flow.
Chemiclean is just band-aid but it works well. If you don't have a skimmer run an alternative air source and siphon out what you have prior to treatment.

Do your research and follow the instructions explicitly.

 

[BruceOnTheCoast]

Hello Reefers!

I have a 75 gallon tank that first filled on October 5. My current parameters are:

Salinity 1.23
Nitrate 4.4
Phosphate 0 (Hanna Low range)
Alkalinity 9.32
Nitrite 0
Ammonia 0

I have notice alkalinity rising, and nitrate dropping, have never got a reading above zero on phosphate.
Tank has 5 assorted small fish, some Zoa's, and a Duncan, all of which seem fat and healthy. Shortly after tank was cycled and 2 clowns added, went through a brown diatom phase, added snails and it went away. Now I have this black/charcoal colored matt all over sand. If it was reddish I would say its cyano, but the black color is throwing me off. I have vacuumed it out but it came back hard, been there about three weeks. Also seems to me entirely on sand, not rock.
The tank is one that I had to take down about 5 years ago, when i set it back up I used about half new dryrock, and the rest is old live rock from before, which had set dry for several years and then cleaned before new setup.
If its Cyano, I have dealt with it before and there are plenty of resources and advise here to control, but could it be something else?
Thanks,
Bruce

 

[BruceOnTheCoast]

2 votes for Cyano so far, even though its black. I want to avoid chemclean as of now, and try to fix environmental issues. Should I be concerned about dropping Nitrate levels and zero Phosphate? Nitrate was consistently between 7 and 9 until this week.
I do have sump with sock, skimmer, and uv filter.

 

[dwest]

I’d be a bit nervous running zero phosphates measured with your Hanna. I would likely add some measurable amount of phosphates and continue to monitor nitrates. Alternatively, you could stop collecting skimmate and remove filter socks for a while and see.