"tan dandruff" on my sand bed

[hughem]

There are patches of, what I can only describe as tan dandruff on my sand bed. It could be residual dead tissue from frozen food cubes (shellfish mostly) that I guess the fish either don't eat or don't breakdown. At night, I see an army of 'pods working on the stuff, but they aren't reducing it very much (although it doesn't seem to be INCREASING either).

I don't think its any kind of algae because it isn't attached to anything. When I drop a cleaning magnet or something else on the sand, it is easily displaced and swirls up in the water. It accumulates in areas of light and shadow so lighting isn't a factor. I examined it under a microscope -- it just appears to be fiberous tissue

Although I have numerous bristle worms and countless 'pods, there are only a few detrivores larger than this. Could it be that the few small hermits I have can't keep up with this stuff? Would it help to add a number of brittle stars and/or cucumbers? If I directed powerhead current at it, it would stir it up, but where would it go? There is some in the refugium too, and it doesn't go away there either.

My concern is that, while this stuff sits on the surface, the 'pods aren't stirring the sand, just this fiberous waste on top of it. I think the sand beds are still working (zero nitrates when caulerpa alone didn't achieve this), and the RO/DI unit helped too. Its also unsightly!

Specs. 125ga. + 16ga. refugium, 2 x 250watt 6500k MH, 2 x 96watt VHO actinic
79-81F 8.27-8.46 PH Alk 1.1meq/l Calc 290
Ammo, Nitrites & Nitrates all zero
The Salifert nitrate test shows the slightest tinge of purple, but not close to 2 (.2), so I know its working, but nitrates are virtually gone.

Any ideas?

[Greg Moore]

Your alk and calcium are brutally low! Hope you don't have much coral in there?

It could be calcium carbonate that has precipitated out, especially since your levels have been depleated by something. Usually 'snow' is whitish or grey but I have had tan show up in my tank. It is usually very 'dusty' in the way it can be moved around. Fish/coral/invert waste of course is also the same, tan, dusty and very 'light'. Calcium precip isn't going to hurt anything I don't think, just looks bad, fish waste of course will lead to higher nitrates and possibly some other good algae food.

Greg

[hughem]

Calcium precipitate. I hadn't thought of that. I do have calcium crust on the feather caulerpa in the refugium, but this is bright white and hard. The "tan dandruff" is much darker than "white" and fiberous/flexible. Would calcium behave like this?

I suppose calcium could act as a binder on other residual bio-matter, bringing it together in larger pieces. I went to Jeff's today, partly to meet some of the Aqualink reefers and partly to get some more substrate critters. I got 3 sand stars, 2 black brittle stars and an urchin.

Maybe I'll pull another sample of that junk out of the tank, prepare it on a slide and look at it again. If I can isolate a sample of it, I can test it for mineral content. What disolves calcium? LimeAway? If this disolves the sample, it probably isn't bio-matter afterall.

Thanks for the suggestion.

[rayjay]

FWIW, I get a tan coloured residue on the bottom of my bare bottom berlin style tanks, which is residue from the rocks due to micro life boring through the rocks. If you collect some and place it in a jar and shake it up, the residue would sink resonably rapid because of it's density. I'm sure it's also in my substrate bottomed tanks, but settles into the substrate which is not a fine as I'd like it to be.

[rshimek]

Hi Hugh,

I suspect this is just standard "detritus" that is not getting worked into the sand bed and processed there as it should be.

My suggestion would be to get a couple of detritivore kits - one each from IPSF and Inland Aquatics and let them get established.

Also, as other posters have noted you need to bring the calcium and alkalinity up. Other things than corals depend on those levels.

:D

[Greg Moore]

I agree, now that you describe it further, detritus is probably the source. Calcium snow would not be 'flexible in the manor you describe. As for the colour of calcium snow, it would depend on how it formed and what it picked up as it went. Picture the calcium deposits in your kettle, usually brown to tan because of iron etc.

Get some clean up crew additions and vacuum out what you can before it adds to algae.

Greg

[Vilas]

FWIW, I had a ton of that stuff myself - up to a quarter inch of it in some places. I'd see it shooting out of the live rock, I called it "rock poo"
I got my ipsf detritivore kit last week, and it's pretty much all gone. Plus, bugs are a blast to watch. :)

[AJReef]

hughem,

Sorry to break it to you, but adding those sand stars -- if they're of the burrowing type, generally whitish with darker markings -- may quickly cause your sandbed some major problems. I had one of these stars in a 40G reef about six years ago in San Diego, and the thing kept the sand a pristine white, as advertised, but only because it devoured everything in the sandbed: every worm, every bit of detritus, everything. Then it starved and died. Then I learned about functioning sandbeds and now allow only mopping cucumbers to do the upper-layer cleaning.

Those stars may remove everything you put in your sand to make it efective, so be warned.

--Aaron

PS
I have good luck with the small Fromia sp. stars in my reef now, if keeping stars is of interest to you. Fromia seem pretty harmless.

[hughem]

Thanks for the responses and warning about sand stars. I had a substantial detrivore population, then got a kit from IPSF to boost it.

I have tons of 'pods and bristle worms. Dozens of baby bristles on the glass day and night. After lightout, the sand bed looks like a horror movie! There are thousands of pods scurrying everywhere and bristle worms streaching out from every rock. The problem is that they can't keep up with it, and it doesn't get worked into the sand bed.

Despite this, my nitrate levels are virtually zero. There is the slightest tinge of purple in the test but it doesn't approach even 2 (which would be .2 at that level).

I added some Southdown sand to fill in some holes the return water made in the back of the tank, and next week I will add some more. Eventually I hope to get the whole bed to 6".

Meanwhile I am attacking the calcium & alk issue.