# Soil Depth Question



## jshimola (Mar 6, 2017)

I'm new to planted tanks (and the forum). I am in the process of setting up a 29 gallon dirted tank which will be using HO T5 lights and DIY CO2.

Some background: I originally bought a bag of MGOC, however the only bags I could find were kept outside. When I opened the bag it smelled strongly of sulfur so I decided not to use it. As an alternative, I used store bought topsoil which had an ingredients list including peat moss, bark, and compost. I rinsed the soil to remove large particles, made a huge mess, and then mixed it with diatomite. I added this to the bottom of the tank, capping it with a medium size black gravel. And keeping with the mess, I mistakenly added this to a full tank, making a nice brown water column. So I drained the tank and added water more carefully on the second attempt.

Apparently I'm not very good at eyeballing measurements (the deep brown water didn't help either)... Instead of using 1 inch of soil/diatomite mix I ended up with 2 inches. Given my gravel cap, I have 4 inches of substrate. Based on previous posts, this sounds like I'm going to end up with anaerobic substrate. Between the rotten MGOC and filling the aquarium twice (plus the dearth of aquarium plants in my area), I am getting a bit frustrated and it is making me reluctant to restart. However, I'm thinking this is the best route. 

The only things that might reduce the probability of anaerobic pockets in my situation would be my use of medium sized gravel as a cap, my use of a 1:2 mix of topsoil to diatomite, and that topsoil should have a bit less organic material than potting mix. In your opinions, are these factors enough to overcome the depth of 4 inches? Alternatively, is there an easy way to keep the gravel separate from the lower layer when removing it?


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## Willcooper (May 31, 2015)

If I were you I would read the sticky in the substrate forum. I would also YouTube Dennis Wong using dirt substrates. The sticky talks about mineralizing topsoil and Dennis Wong talks about depth and misconceptions of using dirt. In my opinion you need to start over to avoid long term headaches using the information from the sticky and the YouTube video. 


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## jshimola (Mar 6, 2017)

Thanks for your replies! I am going to tear it down and start again. But I did have a followup question for future reference. The Dennis Wong video states that the substrate can be deep as long as it is setup properly. I'm not sure from the video if 'properly' meant the layering he refers to later (with the organic matter close to the top) or some unmentioned other technique. How do aquariums with deeper substrates reduce the negative effects of anaerobic pockets?


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## roadmaster (Nov 5, 2009)

Plant's can transport oxygen to the area's surrounding the root's and thereby creating unfavorable condition's for anaerobic bacteria or gases to build up.
anaerobic condition's only happen in low Oxygen environment.
Would also submit that should the gas hydrogen sulfide escape into the water column ,the oxygen in the water render's the gas into largely harmless sulfates.
Some studies suggest that we need both aerobic and anaerobic bacteria present in the substrates.
I have run some pretty deep dirt substrates without issues.


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## Willcooper (May 31, 2015)

jshimola said:


> Thanks for your replies! I am going to tear it down and start again. But I did have a followup question for future reference. The Dennis Wong video states that the substrate can be deep as long as it is setup properly. I'm not sure from the video if 'properly' meant the layering he refers to later (with the organic matter close to the top) or some unmentioned other technique. How do aquariums with deeper substrates reduce the negative effects of anaerobic pockets?




I haven't ever done a deep dirt substrate so I can't say from experience but if you mineralize the soil it should eliminate much of the organic material that isn't available to the plants anyway. Well not until the bacteria converts it anyway. Mineralizing just speeds up the process so you shouldn't have to worry about it as much. Not a sarcastic question but have you ever heard of anybody killing their livestock due to aerobic pockets? I haven't. But I did see something from the big Al's channel where he used a block of porous material meant for anaerobic bacteria to denitrify so that might be an option to put at the bottom of a deep dirt substrate. It was on the 265g build project. 


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## BigMek (Dec 6, 2016)

My understanding is that anaerobic pockets are only a problem if you disturb a bunch of them at once (Hey, I haven't stirred my substrate in a while, let's do it all today) and release a bunch of hydrogen sulfide which gasses your aquarium to death. In general anaerobic pockets are good for your aquarium since they host denitrifying bacteria which can convert nitrates either into nitrites (this is good, plants uptake nitrites better) or free nitrogen gas. Either way they help slow the buildup of nitrates, which is how us Walstad folks can go so long between water changes.


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