[Caesar Augustus]

As all of you know, I've been going though hell with this friggin DSB. Just now I've been having some water issues and I've noticed some new colors in the DSB. There are some green streaks and some brown and some brownish green patches in the bed that seem to be more apparent the last few days Thoughts? Ideas? Beer? Anyone?
Augustus

[Reefland]

Beer please!

Are these colors on or in the sand bed (as can be seen through the glass)?

[Caesar Augustus]

They are in. As in can see them through the glass. The top o the bed is peachy. FYI I'm sippin a cold one right now and I must say Scott you had a fine idea there
Augustus

[Reefland]

The algae in the sand bed is quite natural and to be expected, in fact it is a good sign of life in it. You will probably see green and red cyanobacteria but this is nothing at all to worry about.

[Caesar Augustus]

Thanks for the feedback Scott, I'll be contacting you with my next question, problem, or mental breakdown shortly
Augustus

[Reefland]

You know where to find me.

[BubbaWPB]

The only color I think you have to worry about is big black nasty-looking blobs... if I'm not mistaken, that's an indication you're getting hydrogen sulfide production... other colors are ok.

[Caesar Augustus]

Thanks bubba, Its mostly green. lots and lots of shades of green. I'll keep an eye out for black. BTW If I started to see some...........what the hell can you do about it? You sure wouldn't want to desturb the DSB going after it, if ya catch my drift.
Augustus

[Ninong]

Originally Posted by BubbaWPB

The only color I think you have to worry about is big black nasty-looking blobs... if I'm not mistaken, that's an indication you're getting hydrogen sulfide production... other colors are ok.

Hydrogen sulfide production is not only not detrimental, it is a requirement of a functioning deep sand bed.

Rather than type out a 2,500 word explanation, I think I'll just direct you to Dr. Rob Toonen's excellent two-part article on the chemical reactions that take place in deep sand beds: Part I and Part II.

Happy reading!

[Ninong]

Originally Posted by Caesar Augustus

Its mostly green. lots and lots of shades of green. I'll keep an eye out for black. BTW If I started to see some...........what the hell can you do about it?

If you're looking at the upper layers of your deep sand bed through the glass wall of the tank, you should see various shades of green, red, pink, purple, brown, beige, gray and, below the obvious redox discontinuity layer, darker gray and then black.

The colors are beneficial bacteria (mostly beneficial cyanobacteria). That's an indication of light penetration and of an oxidized environment. As you get deeper, the oxygen gets scarce and the colors turn gray. You should see what is called the redox discontinuity layer, below which there is little or no oxygen (reducing environment). The black areas are produced by hydrogen sulfide.

There is no need to worry about hydrogen sulfide rising up through the sand bed and nuking your tank. As the hydrogen sulfide encounters oxygen above the RDL, it will be oxidized into harmless sulfate. This does not mean that you should stir up the black layers at the bottom of the sand bed. This is definitely a no-no.

The RDL (redox discontinuity layer) fluctuates up and down depending on conditions. It's usually a sign of potential trouble ahead if this line starts to come very near the surface all across the tank. That means that oxygen is not penetrating very far beneath the surface.

The RDL in sediments in the wild can be as near as 1/2" beneath the surface in stagnant areas or it can be 2 or 3 inches beneath the surface.

P.S. -- I'm assuming that your DSB is at least 3" deep? A depth of 3"-4" is about the minimum you need for a DSB. You can get some denitrification benefits from a shallower sand bed but it may not be a fully functioning DSB. It's possible to get a functioning DSB with as little as 2-1/2"-3" but that's not as reliable as 3"+. A 4" DSB will definitely work as a fully functional DSB and once you get to about 8"-10" depth, new chemical reactions take place that you don't get in DSBs of less than 8" depth.

This is not to say that you can't have a 2" sand bed if that's what you prefer. It just wouldn't function the same as a 3"-4" DSB. You can't really call it a DSB unless you have an obvious RDL with aerobic (oxic) layers above and anaerobic (anoxic) layers below.

[Caesar Augustus]

Thanks Ninong, Yea shes deep alright. About 4-5 inches.