# What happens to deep substrate too deep?



## Rtifs (Nov 6, 2009)

Ok. I set up my first NPT last weekend. 75g, unfertilized topsoil (seems to have lots of compost). It’s actually not completely setup yet… needs more plants, but I’m trying to get the ground cover plants (dwarf hairgrass (Eleocharis acicularis) and pygmy chain sword (Echinodorus tenellus)) a head start over the amazon swords that I’ll be moving into it. 
My question is what happens if the soil is deeper than 1”? Mine is probably 2” and maybe 3” in a couple spots. This soil is quite fluffy though, so it could probably compact down by an inch. I’ve read “Ecology of the Planted Aquarium,” but don’t remember what happens with deeper substrate. I’m assuming deeper substrate is in danger of becoming anaerobic and thus toxic. Are there any plants that can help aerate the soil other than lilies (too big for aquarium environment)?


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## mudboots (Jun 24, 2009)

> My question is what happens if the soil is deeper than 1"? Mine is probably 2" and maybe 3" in a couple spots.


My first attempt at an npt was using organic substrate ranging from 2 to 4 inches deep. The entire tank was toxic from the methane and hydrogen sulfide gas and so on. I had to completely tear down the tank, and was thankful that it was only a 20 gallon and not the big tank.

The other npt tank I set up, that has not had any toxic gas issues, has about .75 inches of organic substrate (loose and "fluffy") with another .75 inches of a sand/gravel mix.



> This soil is quite fluffy though, so it could probably compact down by an inch.


If you compact your substrate you restrict aeration and promote the anaerobic conditions that will lead to toxic gas production.

Right, wrong or indifferent, my humble suggestion would be to re-do the substrate to where you have between .75 and 1 inch (but no more than that) of the organic substrate, with a similar depth "cap" and not let your totol substrate depth be greater than 1.8-2.0 inches.


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## HoldingWine (Oct 7, 2007)

You might also want to measure the substrate depth accurately with tape measure or the like. I noticed when I guestimated soil depth, I often ended up overestimating how deep my soil was. If the deepest part isn't over 1.5", I wouldn't worry about it, but if you did see spots that were in the 2-3" range, you might want to consider redoing the tank.

Definitely find a few Malaysian Trumpet Snails if you haven't already. They're great for aerating the soil. I'd recommend throwing in those sword plants, too. They can help suck up some of the excess nutrients from a large soil depth.

How about a picture of the tank?


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## dwalstad (Apr 14, 2006)

Rtifs said:


> I'm trying to get the ground cover plants (dwarf hairgrass (Eleocharis acicularis) and pygmy chain sword (Echinodorus tenellus)) a head start over the amazon swords that I'll be moving into it.
> My question is what happens if the soil is deeper than 1"? Mine is probably 2" and maybe 3" in a couple spots. This soil is quite fluffy though, so it could probably compact down by an inch. I've read "Ecology of the Planted Aquarium," but don't remember what happens with deeper substrate. I'm assuming deeper substrate is in danger of becoming anaerobic and thus toxic. Are there any plants that can help aerate the soil other than lilies (too big for aquarium environment)?


I doubt that your small, ground cover plants will grow well enough to help stabilize a 75 gal with a deep organic substrate. I would plant large robust plants (Red Tiger Lotus, several Amazon Swordplants, Giant Val) as soon as possible. You'll want to encourage emergent growth. For these plants, you'll need very intense lighting.

Folks, this is why I generally recommend 1" of soil and 1" of gravel or sand. If you go with a deeper substrate, you need to match it with intense lighting and robust plants right from the get-go.


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## Dustymac (Apr 26, 2008)

dwalstad said:


> I would plant large robust plants (Red Tiger Lotus, several Amazon Swordplants, Giant Val) as soon as possible.


I didn't know better when setting up my npts so naturally my thought was if 1" is good then 2" is better. Fortunately the initial plantings included lots of Swords and explains my success so far. But I'm wondering if there is still a possibility for problems in areas of my tanks where the Sword roots might not reach?

Jim


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## Perianth (Mar 17, 2009)

While we are wondering, I have been wondering if deep substrate produced hydrogen sulfide is hazardous to us humans. I know it can be fatal in extreme cases such as at oil rigs (have heard of a public evacuation because of that), but I have also read exposure causes visual problems. I don't believe I want any of it in my house. Any body have any facts on what the danger is?


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## Diana K (Dec 20, 2007)

No facts or studies, but my guess is that a house is too well ventilated and the production is too small to cause problems. 
This may not apply to an enclosed fish room, though, where you are minimizing air exchange to maintain temperature.


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## dwalstad (Apr 14, 2006)

Perianth said:


> I don't believe I want any of it in my house. Any body have any facts on what the danger is?


H2S (hydrogen sulfide) gas has been shown to be more toxic than ammonia to mammals.

That said, plant roots and bottom-dwelling fish are on the "front-lines" from any H2S generated by organic substrates, not you. Many aerobic bacteria quickly oxidize toxic H2S to harmless sulfates. By the time any remaining H2S escapes into the air, its concentration is severely diluted.

Unless your house positively reeks of the rotten egg odor, I wouldn't worry about H2S as a poison to you.

However, you do need to monitor your fish and plants. Are plants floating to the surface with blackened roots? Are bottom-dwelling fish becoming lethargic?


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## Rtifs (Nov 6, 2009)

*Re: What happens to substrate that's too deep?*

Ok. Well no worries, since I don't have anything but water and plants in it now. I'm in the process of moving, and the tank is at the destination. I won't be there full time for close to a month, hence the lack of anything in the tank that needs regular feeding. My plan was just to try and get the substrate through the worst of the "chaos" break-in period before needing to move my fish in. Unfortunately, when I set it up, my time was very limited and I was in an incredible hurry. That's why I was careless with the substrate depth.

I may be at the apartment again in two weeks, so I can drain and redo the substrate then. Here is a pic I took today after adding one large and several small swords. The water's a little cloudy, but I'm not worried about it at the moment&#8230; especially if I'm going to drain it soon.


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## Qwertus (Oct 14, 2008)

The substrate looks average to me for a tank that size. It isn't too deep.


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## dwalstad (Apr 14, 2006)

Tank looks promising. Could use a water change to remove cloudiness and a few more plants, but its not a bad start. If the plants grow well, it won't matter that the substrate is a little deep in spots. 

One thing.... I would move the Amazon Swordplant out of the corner (should be easy to move while its still small). I would put it between the 3 rocks-- or somewhere more towards the center. Here, it will get more light and grow to its full magnificent potential. One robust Amazon Swordplant can prevent all kinds of start-up problems in an NPT.

You may have to trim it regularly later on, but this is far better than having algae problems, substrate melt-downs, etc in a new tank.

Good luck!


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## Zapins (Jul 28, 2004)

I normally use soil that is 2 inches deep. Though I have used it up to 5 inches thick without problems. I have MTS though, and high light and CO2, so any of those (or all of them) seem to prevent anaerobic conditions.


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## brenmuk (Oct 7, 2008)

Is this rule of 1-1.5" of soil with 1" of gravel/sand only applicable to tanks with soil under layers?

The reason I ask is that there are plenty on the aquascaping scene that create areas of the tank with the substrate piled up to 5-6".

See an example of an Oliver Knot demo at The Green Machine, he is using ADA Nile Sand, ADA Aqua Soil Amazonia, and Tropica Plant Substrate sandwiched between 2 layers of Aqua Soil:

http://www.thegreenmachineonline.com/Aquatics/Aquascapes/oliver-knott-at-the-green-machine/


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## JeffyFunk (Apr 6, 2006)

brenmuk said:


> Is this rule of 1-1.5" of soil with 1" of gravel/sand only applicable to tanks with soil under layers?


Generally speaking, yes. The reason you don't go much deeper with a soil sub-layer is to prevent the soil from going too anaerobic. The REDOX potential of the soil generally decreases the further down you go (since you have less oxygen available to act as an electron acceptor) and it's been found that 1-1.5'' is about the lowest REDOX potential you want.

In high tech tanks, like the ones Oliver Knott tends to make, these tanks are usually made with a soil substitute (like ADA Aquasoil) which has been formulated to be more granular and not compact as much as soil. Also, these high tech tanks also use heating cables to promote water movement in the substrate which helps to prevent the REDOX potential from becoming too low. (It's amazing what money can help compensate for...lol)

As Zapins has stated, he has used a deeper soil substrate in his tanks, but I think the fact that he also injects CO2 (among other things) helps to protect the plants from effects of a low REDOX substrate.

And as Diana Walstad has stated, amazing plant growth by plants with large root systems such as Swords, Vals & Lotuses will also work well in deep soil substrates.


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## Emily6 (Feb 14, 2006)

What factors other than substrate depth cause the soil to become anaerobic? Mine's not deeper than an inch with about the same in gravel (and I did measure as I went since I made this mistake once, but too shallow). My biggest aggravation is that the gas bubbles are causing mounds in the substrate, displacing the gravel and releasing sediment into the water. Now the soil and gravel are getting mixed. :-/


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## dwalstad (Apr 14, 2006)

Emily6 said:


> What factors other than substrate depth cause the soil to become anaerobic?


How much the organic matter has been decomposed. Fresh organic matter (tree leaves, lawn clippings) is fast-food for bacteria. As bacteria feast on it, they will consume all oxygen and make everything severely anaerobic.

A month or two later, the organic matter will be digested and no longer fast-food. If you add it to the aquarium then, it will not generate severely anaerobic conditions.


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## Johnriggs (Jun 26, 2009)

Small areas of my soil has gone "sour." My tank is small, a six gallon. I found this out because one of my dwarf African frogs keeps trying to crawl out of the tank. This usually means something is wrong with the water. Since ammonia, nitrites, nitrates, and Ph were all fine, I poked the substrate and lo--in one area stinky bubbles popped out. If my soil is burping HS2, no wonder he's trying to leave the water.

I have a red water lily, some swords and a few straggling sags, as well as a couple of apogenatons and anubias. I have a lot of floaters such as water sprite and guppy grass too. Lately my plant growth has been slow, I assume because of fall and winter. I've had little luck getting sags or any other grasslike plants to thrive. Any suggestions to aerate this stagnant area?

J


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## dwalstad (Apr 14, 2006)

Johnriggs said:


> Small areas of my soil has gone "sour." My tank is small, a six gallon. I found this out because one of my dwarf African frogs keeps trying to crawl out of the tank. This usually means something is wrong with the water. Since ammonia, nitrites, nitrates, and Ph were all fine, I poked the substrate and lo--in one area stinky bubbles popped out. If my soil is burping HS2, no wonder he's trying to leave the water.
> 
> I have a red water lily, some swords and a few straggling sags, as well as a couple of apogenatons and anubias. I have a lot of floaters such as water sprite and guppy grass too. Lately my plant growth has been slow, I assume because of fall and winter. I've had little luck getting sags or any other grasslike plants to thrive. Any suggestions to aerate this stagnant area?
> 
> J


Your frogs are telling you something. I would add an air-stone immediately. 
Also, you need to keep a temperature that allows plants to grow during the fall and winter.


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