# Just soil without gravel cap?



## UnderwaterGuineaPig (May 29, 2014)

Has anyone done a tank with just soil and no gravel or sand cap? I've just submerged a layer of John Innes no. 3 potting soil and it settled really quickly with the water above clearing nicely. So now I'm wondering whether the gravel cap is purely for aesthetic reasons or whether it serves another function.

How would burrowing snails and cories etc go in a soil only bottom?


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## Zapins (Jul 28, 2004)

I haven't set up a tank like that from the start, but I've seen what a mess happens when the cap is removed from a section of soil and the soil is exposed to the water column. The first thing is the soil gets everywhere all over the tank and looks terrible, then you get nasty algae problems.

Usually you want to add soil first when the tank is empty, add the cap on top and then slowly and carefully fill the tank with water so you don't disturb the soil underneath. The idea is to keep all the nutrients and mess contained and prevent it from getting all over the place and promoting algae.

Burrowing snails like Malaysian trumpet snails are a great idea (a necessity in my opinion). They act like earth worms and keep the substrate aerated which prevents the very real possibility of anaerobic substrates. 

You want to avoid burrowing or digging fish, they will get soil everywhere while the snails will not.


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## qwe123 (Jun 15, 2011)

Funny this should come up right after a thread on TPT about the same question:
http://www.plantedtank.net/forums/showthread.php?t=649514

Yes, the cap serves more than aesthetic reasons, and makes the job a whole lot easier, but it is possible to go without if that's what you really want. I'd imagine part of what would make it possible would be avoiding fish like cories, however, as dirt would end up everywhere...


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## Tugg (Jul 28, 2013)

Disclaimer:  I have no experience with soil yet.

But wouldn't a hole in a cap have a different result than a tank that was capless from the start. In a capless setup using MTS, I would think the first inch of soil would have stabilized during the initial cycling of the tank. The filter should be able to keep up with anything it's leeching. In a busted cap, you're exposing very rich soil that has been previously trapped.

It would also depend on how the tank is planted. If its heavily planted tank you may have a layer of thatch thick enough to serve as a cap couldn't you? Though you would probably need to dry start something like this.

In the long run, don't the caps of soil tanks eventually get mixed in? We can do things to slow this, but at some point you're bound to have as much organic matter in the cap as you do the lower layer.

It would be an interesting experiment to take a tank and put in MTS that has been broken down good and screened and mixed with 50% Safe-T-Sorb and see how it works, with and without digging fish.


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## Michael (Jul 20, 2010)

In general I agree with Tugg, but Zapins makes a good point about keeping the nutrients in the substrate and not in the water. This would be a bigger problem in new tanks, and those with very fertile artificial soils as opposed to natural or well-prepared soils. Remember, natural soils rarely have an organic content greater than 25%, leaving plenty of sand, silt, and clay to anchor the plants.

What is in John Innes No. 3? We don't have it in North America. Most potting soils for terrestrial plants are MUCH more fertile than the soils that work well in aquaria.

I will set up a Walstad bowl without a cap and see what happens. Stay tuned for reports!


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## Zapins (Jul 28, 2004)

qwe123 thanks for the link. I'll follow along and see how it turns out for him.



Tugg said:


> But wouldn't a hole in a cap have a different result than a tank that was capless from the start. In a capless setup using MTS, I would think the first inch of soil would have stabilized during the initial cycling of the tank. The filter should be able to keep up with anything it's leeching. In a busted cap, you're exposing very rich soil that has been previously trapped.
> 
> It would also depend on how the tank is planted. If its heavily planted tank you may have a layer of thatch thick enough to serve as a cap couldn't you? Though you would probably need to dry start something like this.


An interesting point. I can't remember reading any posts about people setting up soil tanks without using a cap. I think it would be very interesting to know what would happen. I doubt the soil would stabilize very much without a cap, but I suppose it does depend on a lot of other factors like planting density and soil type! I'm sure it is possible to get a tank to work without a cap but I think it is much more unstable than a capped soil tank.

I wonder how much the cap impedes the leaching of nutrients out of the soil? Do capped soil substrates last longer than uncapped ones?



Tugg said:


> In the long run, don't the caps of soil tanks eventually get mixed in? We can do things to slow this, but at some point you're bound to have as much organic matter in the cap as you do the lower layer.


In my experience I haven't had too much trouble with the cap mixing with the soil layer. I do usually use fluorite though which is fairly large grained and heavy. Fluorite caps seem to stay separate from the soil layer so well that I am able to recover 90+% of the fluorite cap when I break the tank down. Just recently I shut down a 90g tank that had been set up with soil underneath the fluorite cap for the last 3-4 years. The tank had Malaysian trumpet snails and was frequently replanted. I recovered nearly all the fluorite from the top.

In the past I've tried using pool filter sand a few times which is much finer grained. It also worked as a cap, though there was a little more mixing with the soil than with the fluorite especially as I kept replanting the tank. So I suspect that mixing depends mainly on the grain size of the cap particles. The smaller particles work their way down into the soil leaving the larger ones on top.



Michael said:


> Remember, natural soils rarely have an organic content greater than 25%, leaving plenty of sand, silt, and clay to anchor the plants.


A very good point. I think the current trend of using miracle grow potting soil is not ideal for aquatic plants. Too nutrient rich with easily soluble fertilizers that get washed out rather than bound up and retained like with normal garden soil. Too many organics in the soil leads to anaerobic conditions and a dying substrate. Better to use a clay/sand based soil with less organic material in it.


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## UnderwaterGuineaPig (May 29, 2014)

Thank you all, this has been very interesting. Also thank you qwe123 for posting the link to the other forum.

I can't find the formulation for John Innes no. 3 at the moment, but it is loam based.

I will also set up a little test jar to see how it behaves


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## SBS (Feb 26, 2013)

You should test it with a filter on. I'd presume the soil will settle way easier in time but if any dust goes on the plants for one or another reason like accidental disturbing or the filter flow itself and soil particles lands on plant leaves then you'll have the least Black beard algae very fast and you can't have carpet plants for that reason. I certainly don't think it's worth trying that way in a tank with flow at least. 
It may work in a filterless jar though.


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## Phoenix1307 (Jun 1, 2014)

One additional point about the cap: it tends to keep the mulm in the cap where it's available to bottom-feeders and snails, which as has been pointed out, are highly desirable, if not a down-right necessity.

I haven't checked at the store yet, but Miracle-Grow soil, does it or does it not contain some added fertilizer? I specifically avoided any and all soil mixes that contained artificial fertilizers in my soil choice, and so went with Kellogg's organic soil. It contains cow manure and bat guano, and probably other organic fertilizers, none of which will "burn" plants. Organic fertilizers are naturally slow-release, and yes, it did stink for a couple of weeks, but water changes, three times a week, eventually cleared everything up. The water I took out of the tank was used on potted plants which appreciated the organic "tea." If there's any smell to the water at all now, it's the organic smell of soil, as the manure component no longer smells.

According to "Ecology of the Planted Aquarium" by Diana Walstad, whereas the artificial "Japanese" additives will usually last for about two years, regular soil will last for at least 8-10 years, and perhaps longer. I might also add 40 lbs of Kellogg's was well-under $10. According to Walstad, even garden soil will work. I'm exceptionally pleased with my tank. Plants are growing like weeds, crazy fast, and everything seems to be in balance. I also added UV to control pathogens that may come in with new fish, with the side effect that it also controls algae in a rather "natural" way, rather than having to use chemicals, etc.


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## Michael (Jul 20, 2010)

Miracle Grow Organic Choice has poultry litter in it, which is undesirably high in nutrients. Other MG products do have synthetic fertilizers. High fertility is great for terrestrial plants, but can be a real problem in aquaria.


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## Zapins (Jul 28, 2004)

Yes, as mentioned above miracle grow is not suitable for aquariums. I really don't know who started using it and why people recommend it. I have seen so many posts where that substrate has turned anaerobic and killed off plants. It might work sometimes, but in general it just isn't a good match for growing aquatic plants.


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## Skizhx (Oct 12, 2010)

To the best of my knowledge, it's recommended because it's available. We know it's terrible soil for our purposes, but because it's so consistently terrible for everyone everywhere, it's been through a lot of trouble-shooting, and we've pretty much identified its problems, so we know how to trouble-shoot it better than anything else.

Does this mean it's good? Of course not... But... I think that's about as far ahead as the hobby has looked here.


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## Tugg (Jul 28, 2013)

I think it was because its nationally available and rather consistent. What happens is though, is people get impatient and don't prep it correctly by rinsing and mineralizing it first. Then they also don't cut it with an inorganic mix like Safe-T-Sorb.


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## Michael (Jul 20, 2010)

The last two posts are right on!


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## UnderwaterGuineaPig (May 29, 2014)

I set up a little test bowl with just soil about 5 days ago but nope, the suspended particles are just not settling... There must be a fair bit of clay in the John Innes no. 3 soil I'm using. I think I'll pour off the water and put gravel on top, then refill carefully and see what a difference it makes.


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## Michael (Jul 20, 2010)

Most clay soil particles will eventually settle, except for the very smallest type. These are called colloidal clays, and the particles are so small that the random movements of the water molecules are enough to keep them in suspension. The native soil in my area sometimes has some colloidal clay in it, so I can't use natural topsoil from my garden.


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## UnderwaterGuineaPig (May 29, 2014)

Hi, long time no post. I just wanted to give a little update. I gave up on the initial bowl pretty quickly, but then tried again with a proper little tank, and the soil settled really quickly and it was all going very well.... until the tank developed a leak and I had to empty it!  So in conclusion, a tank with just soil seems to work quite well, provided you don't get a leak in it!  I might give it another try soon. I have a tank with a sand bottom that I'm not too happy with. Maybe I'll change that one over to a soil only tank...


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## Michael (Jul 20, 2010)

Sorry about the leak, but that is good to know about the soil. What kind of plants and fish did you have in the tank, if you got that far?


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## UnderwaterGuineaPig (May 29, 2014)

I had some wild guppies and snails, and echinodorus and cryptocorynes in it. It was going quite well


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## RasmusL (Mar 21, 2014)

It takes time to settle with only soil. I got a aquarium without sand on top and a small tank in the window with some "food" (shrimps and some small insects) which is also with soil only...
It took months before it settled totally and now i can clean and everything without a mess and the water also looks clean...


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## novianto.sutardi (Aug 10, 2010)

i think that it is ok if you want to do that.

however, please 
1. make sure the substrate contains enough clay, just to bind soil particles
2. do the DSM. cover any open surface
3. don't keep bottom dwellers or any fish that can disturb the soil in the first place. i think that shrimp is better at the initial period

still very risky though, 
http://www.aquascapingworld.com/threads/309-my-iaplc-2011-entry.5285/

this guy use a very thin gravel and must prepared for the worst before things stabilized.
or perhaps it is because he doesn't do the DSM part


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