substrate color change

[cath]

The top layer of my substrate (coral gravel) has changed from a light color to mostly dark. Some of it has coraline algae. I first noticed it after I had rid my tank of a disgusting cyano outbreak in August. I've not had any more cyano, but the dark color seems to cover most of the tank bottom. What's going on to cause this? Also, should I put a layer of Home Depot or sugarized sand on top of the gravel. Seems as though most folks here prefer the sugarized on top.



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Cath

-La Dolce Vita

[horge]

Hi cath,

Sand darkening (somewhat brownish?) is almost always linked to a diatom bloom. If you scrape the top layer of sand off, you'll find lighter sand underneath (diatoms love light).

A tank can go through several (though weaker and weaker) pendulum swings before it settles down, and with each reset of the nutrient-vs.-bioload bob, diatoms are among the the first to show their numbers.

They're an exceedingly vital component of most marine systems, to be sure. And they rarely are unaccompanied by other 'darkening' organism populations (dinoflagellates, cyano, algae, etc.)

As for substrate profiles, that's a hot topic for some. I prefer to have area zones of all-rubble and large zones of all-sand (the latter is better for deep, live sandbeds for the sake of faunal migrations).

HTH

[cath]

Thanks, Horge!

What you wrote is a help, although I don't think I described the situation accurately. Or maybe I misunderstood your description. Is diatom bloom a brown film covering the gravel? If so, that's not what's going on there. It's more like each individual piece of gravel is a darker shade of tan.

In any case, should I turn that gravel like so much top soil?

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Cath

-La Dolce Vita

Cath sorry I wasnt on earlier, tyong to get through Steven King novel sized voters "pamphlet". As far as the sand grains taking on a darker color, it seems normal in my experience. It may by thin layer of diatoms and or other componenets of the desirable bio film that keeps the sand particles from clumping together like cement. You can add nassarius snails etc to plow the top layers but getting in there ans stirring it by hand is not recommended as our heavy handed efforts to maintain pristine conditions may be hard on the infauna we strive to culture.
Gawd talk about run on sentences. Ading oolitic sand on top of the existing sand bed will make it look pretty for a while but the finer grains will filter down over time. Thats OK as they will be beneficial to the good guys in the sand bed. HTH

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I thought I was me, but we were wrong
email: geeflipr@internetcds.com

[cath]

Wow, Doug! Steven King writes political stuff too Seriously, I'm impressed that you were takling such a publication.

Between you and Horge I've got a good idea about what is happening with the sandbed. I plan to get about 2 doz nassarius workers plus some other snails this Friday. The janitors have been dwindling, and it's time to restock.



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Cath

-La Dolce Vita

Cath this year the voters pamphlet is in 2 volumes, one for candidates and one for the 26 state ballot measures(375 pages) Believe me it was a LOT SCARIER than any Steven King or Clive BArker novel. BTW dont forget to VOTE wed<BG>

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I thought I was me, but we were wrong
email: geeflipr@internetcds.com

[YZ]

Also keep in mind nassarius like to bury themselves and with crushed coral it will be a mighty task for them. I would say get some sugar grade sand. But to help out with your question, I have about 10-15lbs of crushed coral and about 25-35lbs of sand and some of the crushed coral seems to stay on the top and it does stay a darker colorfor some reason maybe micro algae can stick to the pores better who knows??? But then again I have cyano and brown colored cyano whatever you'd like to call it on the sandbed as well, I know I probly need to get some phosphate remover(haven't run any yet) but I'm waiting to take some frags in for credit.

If you have nitrates I'd say throw down some sand, I had 8ppm of nitrate constantly then I put a sandbed in the sump and no more nitrates.