# Is my soil anaerobic?



## vloeien (Nov 16, 2020)

In an effort to remove the perlite and other floating components of my soil, I rinsed it over the course of about a week, stirring it everyday. 

I noticed the soil began to smell badly during this process, so I poured out the water, stirred it a bit more, and put the muddy funky soil into the tank as is. 

The tank is about a week or two old and the plants (plus fish and shrimp) seem to be doing well. However I'm worried I may let the soil go anaerobic during the rinsing process and missed an opportunity to resolve that before capping it. The cap is relatively short--1/2" to 1" max of fine gravel (~3mm). 

About two weeks into the tank's lifespan, I smell a subtle funkiness from the tank, only noticeable when I put my nose to the water surface. It's not nearly as foul as when the soil was rinsing in the bucket, but it's a slightly stronger smell than is coming from my established el natural tank. I don't see more bubbles than normal emerging from the substrate. 

Thoughts? Thanks!


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## maico996 (Nov 6, 2016)

Most likely just part of the normal process of your tank getting settled. Poking the substrate to let oxygenated water into the soil will help. I use my forceps but you can use anything that's long and thin. A chopstick works well. I also used a wire coat hanger that I straightened. If you have any hardscape in your tank it should be sitting on the glass bottom of your tank with the substrate around it, not sitting on top of the substrate.


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## vloeien (Nov 16, 2020)

maico996 said:


> Most likely just part of the normal process of your tank getting settled. Poking the substrate to let oxygenated water into the soil will help. I use my forceps but you can use anything that's long and thin. A chopstick works well. I also used a wire coat hanger that I straightened. If you have any hardscape in your tank it should be sitting on the glass bottom of your tank with the substrate around it, not sitting on top of the substrate.


Thanks for your reply! I'll give that a go--maybe not with chopsticks (or at least the ones I have), because I worry they'll displace too much gravel, but with something thinner like your wire hanger/forcepts.

I do have some rocks, but they're sitting on the tank's glass bottom


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## dwalstad (Apr 14, 2006)

vloeien said:


> I smell a subtle funkiness from the tank, only noticeable when I put my nose to the water surface. It's not nearly as foul as when the soil was rinsing in the bucket, but it's a slightly stronger smell than is coming from my established el natural tank. I don't see more bubbles than normal emerging from the substrate.


There are no missed opportunities! You can always aerate soil in the tank via the poking recommended by maico996. Once bacteria have access to oxygen, decomposition can quickly switch from severely anaerobic to mildly anaerobic, which is what we want.

And if you smelled dangerous H2S (rotten egg smell), you would not use the word subtle.  It sounds like the bucket mineralization process helped speed the decomposition of the soil's most fresh organic matter.

Be nice to see picture of this tank.


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## vloeien (Nov 16, 2020)

So I've been poking the soil at least once/twice per week for the last couple weeks (usually with water changes), and the bubbles have not abated. Every poke releases at least one bubble, and so I end up spending 5-10 minutes repeatedly poking and poking until my arm tires. Sometimes, so many bubbles are released the cap visibly "shrugs," having shed so much air. I'm pretty certain it's not an issue with the cap, as it's 3+mm and even thinner than I usually make it at 1/2" in the front to - 1" in the back.

I have some very young MTS in here. Hoping they can take over this duty soon! 

Is this normal? The tank's about 4 weeks old now. I don't smell rotten eggs...


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## mistergreen (Mar 3, 2007)

Bubbles are normal. If it doesn't smell, it's likely the most valuable CO2. I think you can stop poking.


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## jatcar95 (Oct 30, 2019)

vloeien said:


> I have some very young MTS in here. Hoping they can take over this duty soon!


At least in my tank, the MTS just burrow around the top layer of my cap, they never reach anywhere close to the dirt underneath. Maybe mine are just lazy lol, or there's enough plant cover that they feel protected being exposed. But I've almost never seen them underneath the substrate, just partially buried.


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## dwalstad (Apr 14, 2006)

The deeper soil layers may be too anaerobic for the MTS snails or they are inhibited by small amounts of H2S.
Substrate CO2 buildup is a natural result of decomposition. I only recommend poking if there's a problem--plants not growing. The goal is not to degas the substrate but to counteract a severely anaerobic substrate that is inhibiting plant growth. Truth is I rarely poked substrate in my tanks after setup. I just let the gases bubble up. Vloeine, if your plants are growing okay, I would give your arm a rest!


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## vloeien (Nov 16, 2020)

Roger that! I'll stop poking. Thanks everyone 🙏


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## vloeien (Nov 16, 2020)

dwalstad said:


> There are no missed opportunities! You can always aerate soil in the tank via the poking recommended by maico996. Once bacteria have access to oxygen, decomposition can quickly switch from severely anaerobic to mildly anaerobic, which is what we want.
> 
> And if you smelled dangerous H2S (rotten egg smell), you would not use the word subtle.  It sounds like the bucket mineralization process helped speed the decomposition of the soil's most fresh organic matter.
> 
> Be nice to see picture of this tank.


As requested, a picture of this tank. Thanks for Diana's and everyone's help on this one and the ones that came before it


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## Michael (Jul 20, 2010)

Beautiful tank!


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## tiger15 (Apr 9, 2017)

Only the top 1/2 to 1 inch of any substrate remains aerobic, and it doesn't matter unless you stir up the substrate abruptly to release the anaerobic gases all at once. In my Walstad shrimp bowl, I can see through the substrate and color transition to black ferrous iron and what appears to be blue green algae below the aerobic zone. When I do water change in my big tank when I stir up the gravel substrate, I can observe bubbling up in thick zone or underneath rock, apparently methane or nitrogen from denitrificatin as the gases are odorless. Saltwater folks commonly utilize deep sand to promote denitrification. Roots in planted tanks will deliver some oxygen to the anaerobic zone and gladly utilize Fe2 and other nutrients, so there is nothing to be concerned of if left undisturbed.


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## jake37 (Mar 18, 2021)

I'm not sure i fully agree. While I think the op is over reacting (btw it will smell like rotten eggs if you have a problem); i have had tanks developed very large amount of H2S and nothing grows well in it. I recently replaced the substrate in one of my tanks because of this issue with something slightly larger grain (the tank was 18 months old so i had a lot of time to experiment with it). I'm not 100% sure what triggers the really bad behavior as i had another tank with the same substrate that seem to have largely ignored the issue (maybe the plants grew fast enough for the roots to break up the substrate) but I've mostly decided to go with a grain size larger to allow the substrate more room to aerate. My oldest tank (well oldest substrate since i had to move) is 3+ years and it has no issues other than being coarser grain than i prefer (eco-complete black). The substrate that has given me fits is caribsea moonlight (you can look up the grain size on their website) and i've switch to torpedo beach but it has only been a month so i can't say anything conclusive other than it clumps more than it should. I have a tank with estes stoney river and this stuff is interesting - it is a wee bit finer than torpedo beach but after 2 years it hasn't compacted at all and no gases build up in it - also plants grow really well in it (esp for a low tech tank). My purple aflame is really likes that tank.
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I've made a point of playing with different substrate so when i set up a larger tank i have better idea of what will work for long periods of time.
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One thing i've been considering is running current down through the substrate (basically reverse ugf in which water is being forced down though the plate and then filtered - but i haven't gone that far yet - just a thought).



tiger15 said:


> Only the top 1/2 to 1 inch of any substrate remains aerobic, and it doesn't matter unless you stir up the substrate abruptly to release the anaerobic gases all at once. In my Walstad shrimp bowl, I can see through the substrate and color transition to black ferrous iron and what appears to be blue green algae below the aerobic zone. When I do water change in my big tank when I stir up the gravel substrate, I can observe bubbling up in thick zone or underneath rock, apparently methane or nitrogen from denitrificatin as the gases are odorless. Saltwater folks commonly utilize deep sand to promote denitrification. Roots in planted tanks will deliver some oxygen to the anaerobic zone and gladly utilize Fe2 and other nutrients, so there is nothing to be concerned of if left undisturbed.


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## dwalstad (Apr 14, 2006)

vloeien said:


> As requested, a picture of this tank. Thanks for Diana's and everyone's help on this one and the ones that came before it
> View attachment 73464


A pleasure to look at! I'm so glad this tank worked out for you.


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