flat brown/grey growing all over rocks-

[prin2155]

ok- ive had my tank up for almost 3 years now. there appears to be a grey/brown almost "matte" growing on my rocks. I tried to turkey baste it off and it doesn't come off.

two thoughts: algae died off or GFO/SAND rubbing down the rocks????

Params:
PH 7.9
Sal 35-36
temp 78
nitrates: 16
phos: .02
alk- 8.9
cal 430
mag 1410

running reef mat and gfo/carbon mix. I run the gfo/carbon probably 2-3x per week at night from 8-4am, i have the outflow feeding through filter sock to catch gfo.

or is this just a maturing tank thing?

TIA for any thoughts/help

 

[griss]

Can you post a picture of what, "matte?" Sounds like it could be Diatoms, Dinos or some type of Cyano. @kharmaguru is good at distinguishing between these.

As far as water parameters, the only potential issue I see is your Nitrates are a bit high.

 

[prin2155]

It almost appears like ash on the rocks

 

[griss]

Looking on my phone with my old eyes (even with reading glasses) I can’t really tell what it might be.

Let’s see if we can call in some reinforcements @Timfish @OldReefGuy @wvned @BeanAnimal @reefing102 (apologies in advance, I’m forgetting several others….been fighting a cold).

 

[Misled]

What happens if you run a finger across it? Is it on the rocks or just some?

 

[griss]

What happens if you run a finger across it? Is it on the rocks or just some?

Good thinking Jesse

 

[Misled]

I meant that to say all the rocks or just some of them.

 

[wvned]

Is it on the tops of the rocks but not the shaded areas? If so it's algae. Algae comes in almost all colors.
Under LED lighting colors observed can change drastically.

 

[reefing102]

Honestly hard saying.

The mention of ash look makes me think either detritus or possibly a precipitate of some sort but detritus would blow right off.

My guess would be an algae or bacteria as the rock has aged.

 

[wvned]

I loaded one of the pics in my photo editor and changed the white balance. Nothing came out. The rocks seem to be a uniform shade all over.
Are you looking at Coraline algae?
It covers the rocks and makes them all one color like that. It can look grey or brownish or purple depending on how your lights are set.

 

[kharmaguru]

Looks like a bunch of different stuff (and not really that bad). What kind of grazers do you have? It's best to post pictures with whites turned up.

 

[Timfish]

Looking at your low PO4 and regular use of GFO I'd say it was cyano that was forced to grow real slow and is forming thick mats but it should peel off if you use a flat blade. It it's really stuck to the rock then it's likely some kind of sponge. FWIW I'd raise your PO4.

 

[BeanAnimal]

I have never seen cyano that tough.. but who knows. My guess would be plain old diatoms and brown turf algea.