Black spots in sand

[mrg02d]

Hello all,
I have had some nasty looking sand for some time now, and just got around to asking today.

I have been up and running for 9 months now and have a 20gallon reef tank. My sand bed is 1.5in deep in the deepest spot. The top layer of sand looks yucky. (Light brown with shades of red). Other places are more white. It doesnt look like the diatoms I had before, and is relatively thick. (up to 1cm). Some other places have black regions deeper below.

I dont have any sand sifters except for hermits. I couldnt keep nessarius snails alive in my tank since I only have three small fish and dont feed but once every other day. (two clownfish, one sixline wrasse).

They all died of starvation I assume. Little food makes it to the bottom, and what does is quickly snatched up by my cleaner shrimp, pom pom crab, or the hermits.

How can I keep these nasty spots from forming? How do I deal with them now? Are they dangerous regions of hydrogen sulfide?
Matt

 

[Zer0]

I doubt they are the dreaded toxic bubbles because your sandbed just isn't deep enough. 1.5 inches is nothing compared to +4 inches, which is where those toxic bubbles can occur if you do not have sandsifters. Anyways, do you think it could be cyano? Does it look velvety and is it slimey? Because light brown/shades of red sounds like cyano to me.

 

[mrg02d]

I doubt they are the dreaded toxic bubbles because your sandbed just isn't deep enough. 1.5 inches is nothing compared to +4 inches, which is where those toxic bubbles can occur if you do not have sandsifters. Anyways, do you think it could be cyano? Does it look velvety and is it slimey? Because light brown/shades of red sounds like cyano to me.

Nope, not slimy at all. Very grainy. Doesnt seem to be growing either. Here is a picture of what I am worried about...

 

[Zer0]

Do you have a any powerheads pointing in that direction? Could it be an area that is void of any flow, and detritus is just building up in that area?

 

[mrg02d]

Do you have a any powerheads pointing in that direction? Could it be an area that is void of any flow, and detritus is just building up in that area?

I dont think its buildup, as its under a layer of "clean" sand. The picture is a side view of the sand up against the tank. I have a Koralia power head pointing one direction and the output from a Fluval 305 pointing the other. Detritus could be building up in other places, but these dark regions have me worried. :-(
If it is buildup of toxins, what would be the remedy?
Matt

 

[Zer0]

Uhm, i didn't know that was the sand leaning up against the glass.. Are you 100% positive that the sand depth is 1.5"s? That looks alot deeper than 1.5" and if it is deeper.. then i would be worried. I'm not really sure what it is because i've never seen this before, and if you say your sandbed is only 1.5" then there's no way it could be a build up of toxins. So i would wait for others to input, to see what this might actually be.

 

[Kurt_Nelson]

I really don't think it's anything except for algae growing in the sand right along the glass. I think it's pretty normal for folks that have sand beds that are deep enough to see over the lower trim piece. If you're concerned, you can always "drill" a hole in your sand bed with a siphon tube, an inch or so back from the discolored area and see what the sand looks like back there. My bet is that the sand you siphon out will be normal sand color, with no discoloration, and that discolored sand is just along your glass.

Just my opinion, but I don't lend much credence to the H2S (hydrogen sulfide) killer sand beds. Yes... H2S forms in deep sand beds, but not at the level that is going to kill anything in your tank. H2S dissolves easily in water, so it's not like you're going to see any bubbles rising up through your sand bed. And if could actually see bubbles of H2S in the sand, your main concern would be to evacuate your house because bubbles of pure H2S wouldn't be something I'd want to be around! I've yet to read anything that directly attributes H2S to coral death - it's always anecdotal stuff like "Gee... I stirred my sand bed yesterday and now everything is dead. I must've released H2S."

 

[nxb161]

"Gee... I stirred my sand bed yesterday and now everything is dead. I must've released H2S."

I like the "Gee" added to the front, really sets the tone

 

[mrg02d]

I really don't think it's anything except for algae growing in the sand right along the glass. I think it's pretty normal for folks that have sand beds that are deep enough to see over the lower trim piece. If you're concerned, you can always "drill" a hole in your sand bed with a siphon tube, an inch or so back from the discolored area and see what the sand looks like back there. My bet is that the sand you siphon out will be normal sand color, with no discoloration, and that discolored sand is just along your glass.

Just my opinion, but I don't lend much credence to the H2S (hydrogen sulfide) killer sand beds. Yes... H2S forms in deep sand beds, but not at the level that is going to kill anything in your tank. H2S dissolves easily in water, so it's not like you're going to see any bubbles rising up through your sand bed. And if could actually see bubbles of H2S in the sand, your main concern would be to evacuate your house because bubbles of pure H2S wouldn't be something I'd want to be around! I've yet to read anything that directly attributes H2S to coral death - it's always anecdotal stuff like "Gee... I stirred my sand bed yesterday and now everything is dead. I must've released H2S."

Hello,
I just moved one of my corals that was sitting on the sand bed near the region of blackness and right under it is more black sand! This was a brain coral that has been sitting there for months. The sand looks like blackish grey sand...I wonder what this is? The good news is that the region hasnt been expanding in any way that I can see.
Thanks for the replies! Good to hear that even if it is some buildup, it shouldbnt be dangerous.
Matt

 

[thincat]

Nope, not slimy at all. Very grainy. Doesnt seem to be growing either. Here is a picture of what I am worried about...

Those dard spots are indeed hydogen sulfide and are caused by anorobic bacteria and the lack of sand sifters. Get a sand vacume and slowly do the sand one small spot at a time. Don't do it all at once. You don't want that nasty stuff all over your tank.

 

[mrg02d]

Those dard spots are indeed hydogen sulfide and are caused by anorobic bacteria and the lack of sand sifters. Get a sand vacume and slowly do the sand one small spot at a time. Don't do it all at once. You don't want that nasty stuff all over your tank.

YIKES!!!
So how did this happen? My sand bed is only 1.5in deep...
How bad can this be? Should I worry much about it? How can I prevent this? I dont guess I have a DSB occuring as well do I?
Matt

 

[thincat]

No, it's just a dead spot. It does not look so bad at this point. Just vaccume it up slowly, one spot at a time and it should be okay. It looks like you are feeding to much or that the fishes don't like the food that you are feeding.
What and how often do you feed.

 

[Kurt_Nelson]

Why do you think these particular dark spots signify hydrogen sulfide?

 

[thincat]

I had a couple of these spots in my tank and boy did it smell like rotten eggs. I added a bunch of sandsifters and that corrected the problem.

 

[Mitchell0605]

Where does this hydrogen sulfide come from? How does it form under the sand?

 

[thincat]

anarobic bacteria breaking down detritus in the sand.

 

[Mitchell0605]

Ok fair enough. Now (hypothetically) a person has put in their LR and sand and then cycles etc and gets fish. Nothing ever stirs his sand. Hows does that detrius get there?

 

[thincat]

I believe it's called convexing where very small objects are drawn together. So the very top layer of sand is where the arobic bacteria first break down the uneaten food and then some of that is drawn down where the anarobic bacteria break that down further. Well something like that is where the rotten egg smell kicks in. Sand sifters prevent large spots to developing.

 

[Mitchell0605]

Cool. Thanks TC. I've only got hundreds of worm things that build sand tubes in my sand bed but they do a great job as a CUC and sand stirrers. They plus some bristles worms, and some slugs are my CUC. I couldn't have a better one IMO (and it was free).

 

[thincat]

Yea, I use to love looking at all the creatures in my sand. It is totally amazing!