# Using less than 1" of soil



## aquarium-n00b (May 19, 2020)

I was thinking of the nitrogen cycle in a Walstad tank.

Fish food ultimately turns into ammonia whether eaten by fish or allowed to decompose on it's own. The soil also constantly releases ammonia.

If the plants and bacteria can consume enough of it, then you have a balanced system, but the rate at which your plants consume ammonia depends on:

1. The type of plants you choose
2. The # of plants you can fit in your bowl
3. The temperature of your house
4. The type of light source you have
5. The # and type of fish you get
6. The exact type of soil being used

Because of all these variables, you cannot be sure that your plants and bacteria will take care of all the ammonia.

What if you instead went on the conservative side with the soil? Let's say the rate of ammonia from the soil + fish food is not enough to sustain all the plants you put in the system. Some of your plants and bacteria would die but you would be left with enough plants to keep the water safe for your fish, which is the ultimate goal.

This is opposed to putting in a fixed amount of soil every time, but dealing with the 6 variables listed above. What if your plants cannot take care of all the ammonia? You then have to replace plants or try to add more plants (if there is space), or take out some fish.

It seems like the first method would be easier. I'd love to hear anyone's thoughts on this.


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## SamXp (Mar 12, 2020)

Is the rate of ammonia release related to the depth of the soil bed? Or the surface area? Or both? 


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## hoppycalif (Apr 7, 2005)

I set up a 10 gallon tank a few months ago, and experimented with about a one inch substrate, half soil and half a baked clay floor sweeping compound - Safe T Sorb. It didn't work at all well. The plants didn't grow well. Now I have about 1 1/2 to 2 inches of the same substrate, and it is working very well. My guess is that we need more than an inch of substrate, but not necessarily more than 2 inches.


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## aquarium-n00b (May 19, 2020)

SamXp said:


> Is the rate of ammonia release related to the depth of the soil bed? Or the surface area? Or both?
> 
> Sent from my iPhone using Tapatalk


I would guess it would have to do with both.


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## aquarium-n00b (May 19, 2020)

hoppycalif said:


> I set up a 10 gallon tank a few months ago, and experimented with about a one inch substrate, half soil and half a baked clay floor sweeping compound - Safe T Sorb. It didn't work at all well. The plants didn't grow well. Now I have about 1 1/2 to 2 inches of the same substrate, and it is working very well. My guess is that we need more than an inch of substrate, but not necessarily more than 2 inches.


I saw a popular youtube aquarium guy who did a few no filter tanks. He seems to have a lot of experience with aquariums in general.

In his no filter tank videos he does everything a little different each time. The first time he did the Walstad method with 1" of potting soil and a 1" gravel cap. Another time he used what looked like a bit aquasoil from an old tank so that it was full of bacteria, and then capped it with more aquasoil. Another time he used a bit of tropica powdered soil and then on top of that tropica substrate that looks like aquasoil (but it might be inert like fluval stratum I don't know), and then added old tank water. Another time he took clay from his backyard and baked it, capped it with sand, then added water from an established tank.

In this video he is using the sterilized clay from his backyard with a 1" sand cap and old tank water in lieu of organic potting mix with bacteria in it.






he specifically states to not add that much soil because it will cause algae and it won't help plant growth more than just a little bit. He is also using a 1" sand cap which is more than Walstad recommends...perhaps unknowingly he is stifling ammonia from leaching into the tank...but then there is the also the anaerobic problem.

He also mentions squeezing air bubbles out of the soil to prevent problems later, but I don't see how that relates to anaerobic bacteria...because isn't he producing an anaerobic environment?


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## mistergreen (Mar 3, 2007)

Look up deep substrate on YouTube. They require anaerobic conditions for denitrification, get rid of nitrates. H2S isn’t as bad as it seem as it oxidizes although it smells.

I don’t think it matters how deep the cap substrate and soil are. The system will find a balance.


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## aquarium-n00b (May 19, 2020)

mistergreen said:


> Look up deep substrate on YouTube. They require anaerobic conditions for denitrification, get rid of nitrates. H2S isn't as bad as it seem as it oxidizes although it smells.
> 
> I don't think it matters how deep the cap substrate and soil are. The system will find a balance.


Wait, now i'm confused. I thought anaerobic conditions are to be avoided.
Also, according to Walstad too thick of a cap will lead to anaerobic conditions, which are undesirable.


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## mistergreen (Mar 3, 2007)

Yeah, I would avoid too deep a cap too only because of the smell but anaerobic bacteria serves a purpose too.


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## aquarium-n00b (May 19, 2020)

mistergreen said:


> Yeah, I would avoid too deep a cap too only because of the smell but anaerobic bacteria serves a purpose too.


Seems like in a lot of the threads in this forum, Walstad is commonly pointing out that anaerobic bacteria is the issue with their tank, or a potential issue, or just warning about it in general.

I have read HS produced by it is toxic to fish..or at least that's what is constantly being said in this forum.


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## aquarium-n00b (May 19, 2020)

Here is the latest video based on that same bowl. It's a two month update and things have grown.






He specifically talks about the water column not having enough nutrients for algae. Up until this point he just had some snails in there to get the cycle going.


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## mistergreen (Mar 3, 2007)

H2S is toxic but as long as there's O2, it'll oxidize to SO4. 

Yes, I think that's the idea behind dirted tanks. The nutrients is in the substrate and little in the water column. It's good for root feeding plants. I see stem plants don't do too well though.


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## aquarium-n00b (May 19, 2020)

hoppycalif said:


> I set up a 10 gallon tank a few months ago, and experimented with about a one inch substrate, half soil and half a baked clay floor sweeping compound - Safe T Sorb. It didn't work at all well. The plants didn't grow well. Now I have about 1 1/2 to 2 inches of the same substrate, and it is working very well. My guess is that we need more than an inch of substrate, but not necessarily more than 2 inches.


Well I was thinking 1/2" soil and 1" gravel as opposed to 1/2" soil and 1/2" gravel. A total of 1" is too shallow to plant anything.


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## hoppycalif (Apr 7, 2005)

I don't think the depth of soil/gravel is critical. It can be too much and it can be too little, but the happy middle is pretty wide. I'm basing this on the lack of a lot of threads being started about problems which are caused by too much or too little substrate. I know I have had a wide variety of substrate depths, and only rarely had any plant problems with any of them. Also, when I tear down an aquarium I only get the HS smell when I mistakenly put a big rock or piece of wood on top of the substrate. But my experience doesn't include much of the El Natural method.


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