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Discussion Starter · #1 · (Edited)
The sand along the front and sides of the tank is turning black. What is it and do I need to fix anything? Will it go away?

Tank is an Evolve4 with play sand substrate that's been running for about a month. It has a few baby mystery snails, MTS and a pair of scarlet badis plus lots of plants. There are a couple of O+ tabs in there. I do partial water changes every week and carefully vacuum the sand with a straw to get in the small places (snails poop a lot). There are some blackworms in there but this started before they were introduced to the tank. It also has extra filter media. Before the DHG rooted I stirred the sand every couple of days. I haven't done that recently and am not sure how without uprooting something. I did suck some of the icky sand up and it didn't release bubbles nor did it smell particularly bad - normal mulm smell if anything.

Any advice?
 

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The black sand is likely anaerobic bacteria. There's no oxygen deep in the sand, so bacteria are using other molecules for survival. It's unsightly, but not dangerous so long as you don't disturb it.

Black usually means that you have sulfur bacteria. They will produce sulfur dioxide or hydrogen sulfide gas. If you disturb too much of that substrate, you can release too much gas all at once, which can be deadly to your fauna.
 

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i use whats called arena sand in my 20 long. havent had any problems with discoloration and my tanks been running for about 8 months now. you can find this at just about any place that carries landscaping rocks and gravel. should be able to get a bunch for only a few bucks seeing as how its normally sold by the yard.
 

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It not just a sand thing. It can happen with any substrate really. I have it with my flourite Red. Although its unsightly, I leave it alone for the most part. Typically if you do disturb it and gas is released, once it hits the water column there are really no effects in small amounts. Every now and then when its get too bad I do a deep clean with my python. Disturb as little as possible and infrequently as necessary. Once cleaned the black will go away temporarily but it will return. Lack of oxygen at deeper levels is what causes this.
 

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Discussion Starter · #10 ·
Once cleaned the black will go away temporarily but it will return. Lack of oxygen at deeper levels is what causes this.
Is there any way of preventing it? Or getting rid of it so it doesn't come back? I thought MTS would help, and there are a bunch in there. My other tanks have black substrate and I try hard not to look for problems, so I never noticed if it was there. I was hoping to keep this one light but I'm starting to think it'd be worth the effort to tear it down and change over to black sand.
 

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There's no fix for it? Ugh. Do other types of sand do that, too?
Is there any way of preventing it? Or getting rid of it so it doesn't come back? I thought MTS would help, and there are a bunch in there. My other tanks have black substrate and I try hard not to look for problems, so I never noticed if it was there. I was hoping to keep this one light but I'm starting to think it'd be worth the effort to tear it down and change over to black sand.
Everytime I see it, during my PWC, I take a plastic card and push along the sides between sand and glass...it removes it
 

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Discussion Starter · #12 ·
Everytime I see it, during my PWC, I take a plastic card and push along the sides between sand and glass...it removes it
I've tried running a spatula between the glass and the sand a few times over the past week. It doesn't really do much. This stuff looks a lot like mildew.

If I have time I'm going to tear the tank apart and replace with black sand. At least then I won't be able to see the gunk! Just hate to move the fish - they just got settled in there. <sigh>
 
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