# Soil Cap: Gravel, Sand, or none?



## Rusalka

Hi all,

Like colinsk I'm planning my substrate too, so I was wondering if everyone could give their opinions on what they think the best soil cap is. Gravel, Sand, or none?
Thanks!


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## aquabillpers

You want the fish droppings and other detritus to work their way down into the soil part of the substrate, so that it can provide nutrients as it decays. Therefore a cap should be coarse enough to let that happen. Sand isn't.

If you have a soil substrate without a cap you will probably have murky water most of the time. The cap keeps the fine grained soil in its place.

Bill


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## Rusalka

aquabillpers,

Thanks for your response! Those are all great points. do you use a coarse or fine gravel? how thick is your gravel layer?

Does anyone else have different ideas? I messaged briefly with some people who use no cap at all - and I know there are many people using sand as well right now. I personally have only used gravel in the past and I was pleased with it's ability to reduce turbidity and how it anchored my plants - but I used a layer that was too thick and I am now dealing with a slightly anaerobic substrate so I'm interested in hearing about other caps as well, and the best way to use gravel if I decide to go that way again.


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## bru

I recently set up an aquarium with 2" potting soil and 1/2" EcoComplete. I'm happy with the EcoComplete because it is coarse and seems to provide a good cap. It also is the same color as the soil so you don't have a glaring color discrepancy. However, I found that while planting it is extremely easy to mix the cap with the soil, resulting in suspended sediment and soil on top.

I didn't find that this caused the water to be murky, though. All of the sediment settled. I use a very small HOB filter in my 4 gallon for circulation. In all I'm happy with the result and the EcoComplete certainly provides a coarser consistency at the top layer of the substrate.


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## Rusalka

Thanks Bru! So you prefer a coarser gravel to a fine one?

Any sandcappers out there who want to weigh in for the greater good?


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## cs_gardener

When I first tried a soil underlayer I used regular aquarium gravel as a cap and it was a miserable experience. It was too big too plant in easily and it tended to damage plant stems. I then tried Eco Complete as a cap and it's what I prefer. It's a good size, weight, texture and color. I've also tried Aquarium Plants substrate (it's like Soil Master Select) and it works well enough but it is rather light so it can be hard to keep some plants planted. I've never tried sand so I can't help you there.


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## Juergen

I've tried sand on a bentonite/potting soil mix and it worked.
My next NPT would have a gravel cap again. Although I don't like gravel, it eases my mind. Who knows how a unknown soil will behave?
regards


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## Eugene

I had used with soil both: gravel (4-6 mm) and river sand (1-2 mm). It seems no difference for water and tank's condition.
Some difference is for plants: some of them really do better in substrate with smaller parts (like sand), especially - tiny ones.


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## tames

I have used both sand and gravel. My choice for new setups is sand. For the plants that I like to use it just works much better. Stem plants are very easy to plant, hairgrass loves it as well as marsilea (one of may favorites). The only plant so far I had a little trouble with was a large Sag. (chilensis). It was growing in gravel at the LFS and had a small root system. It came up out of the sand a couple times. After a couple tries, it is now "stuck".

My latest setups - 1 inch of cheap organic top soil (no added manure), added a little crushed oyster shell, and 1 inch of sand.


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## Rusalka

Thanks all for the input! 

Tames, I am finding myself leaning towards sand as well - especially since I've decided to go with a 20 long which is only 12' high and will be planting lots of smaller and carpet plants. From what everyone is saying those plants do better with sand. I think I will go with a very shallow layer of only 1/4 of an inch or even less. That way I can be sure there is lots of aeration happening in the soil. I'm putting alot of pressure on my MTS's to do their burrowing thing - I think they are up to the task. 

Can I ask about the crushed oyster shells? What do they give the soil? 

To everyone - I found some turtle river bed sand from a company called Exo Terra at my local pet store that says it is for an aqua-terrarium. Has anyone used this or know about it?


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## aquabillpers

I just want to comment that "aquarium gravel" comes in several sizes. Some of it is too big to use as a cap, IMO. What I use is 2mm - 3mm in size and it works fine.

I am interested that some have had good luck using sand as a cap. Is the sand the same size that is used in tots' sand boxes, 1 mm or less? For how long was the aquarium in operation? I am wondering how the soil was replenished, since the sand cap would seem to prevent fish droppings, etc., from getting to it.

Bill


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## Eugene

2-3 mm seems to be ideal and universal.

But sand less than 1 mm. is also can be interesting for use and natural (in nature plants grow in it).

I had used such sand since middle of 70-s in some tanks (usially - not big). Also I have one tank with it now.

What are hints:

1. A lot of plants do in such substrate very well. Especially - "carpets", not big crypts, hemiantus etc. Big plants also grow. It's very easy and clean to take routs out if change place of the plant.

2. I never used it with soil in low layer - only some clay & silt mixture added to sand in the 1 sm. down layer or c&s with peat fibres for crypts.

3. The whole depth of small-particle sand must be not more than 3,5-4,5 sm. It only seems thin - now I have a tank with very fine white sand (with very few clay and peat) only 2,5 sm (one inch) deep. And in it there are absolutely happy crypts (petchi, wendta, lutea), marsilea, lileopsis, dwarf saggitaria, eleocharis and rotalas. It seems quite enough for grow and nutrition.

4. The problem of uncarefull start specific to fine sand (especially - white) - algae and cyanobacteria. They can easy grow on it. Sometimes it's enough to ceep some shrimps and dwarf catfish for solution. It doesn't matter eat them algae or not - "bothering" sand they prevent colony grow.

5. The fine sand prevent dirt to sink in substrate. It means that it lay on it and easily go in water. It means that you can keep with such substate not big and gentle creatures and use filter, which can take the small parts. In small tanks it's possible to use even aerolift, but it must be effective enough.

6. The fine sand is beutiful only till it clean. But it's not easy to clean it with typical tubes - it go straight in it together with silt. It is one more reason for very carefull thinking about creatures for such tank and proper filtration.

Beg my pardon for big posting if all these subjects are already spoken about in past.


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## tames

The oyster shell will release calcium carbonate over time. Search this forum using "oyster shell" you will get a lot of posts about it. This is the first time I have tried. it.


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## Juergen

aquabillpers said:


> I am interested that some have had good luck using sand as a cap. Is the sand the same size that is used in tots' sand boxes, 1 mm or less? For how long was the aquarium in operation? I am wondering how the soil was replenished, since the sand cap would seem to prevent fish droppings, etc., from getting to it.


I have used 0,6-1mm quartz from the home improvement shop. Washing losses were accepteble.
The tank was less than one year in operation. Plants, mostly vallis, were still doing well. I redo my tanks regulary, trying something new etc.
Sand is also nice for bottom and detritus eating fish. They can search the dirt for leftovers or consumable mulm.
regards


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## Owain

I just set up a 30 gallon tank using potting soil capped by swimming pool filter sand, and so far I'm very pleased with the result. The sand was very clean, and required no washing and looks very good in the tank. I'm getting a bit of initial tannins leaching from the soil and the wood, so I'll give that a week or so, then perform some water changes to try to clear that up a bit. I'll try to post a journal on the project in the next couple of days, since I took a ton of pictures during the set up.


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## tames

Here is a journal of one of my 20 gal highs I did on 01/01/2009. I too am getting a little tannin right now.

http://bumblesby.livejournal.com


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## colinsk

Rusalka said:


> Can I ask about the crushed oyster shells? What do they give the soil?


Oyster shells are calcium carbonate. Chalk. If the soil gets acidic at all it will disolve the CaCO3 and buffer the soil.


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## Rusalka

colinsk, hmm, i'll look into adding some oyster shells - the calcium may also be beneficial for the shells of my nerite snails. excuse my ignorance but, what would cause the soil to become acidic? I'm also going to put in some bone meal (2-13-0) to bolster the phosphate levels and hopefully promote root growth. 


I'm thinking after all these recommendations that sand is the way to go for this tank. It will be a 20 long so I'm planning on using lots of small/carpet plants, which will do well with sand. I also will have many MTS' who i'm counting on to burrow like crazy! For my Kuhli loaches, I'm planning on making a small area into a 'kuhli playground' with just 1/2 of sand and a slate cave perhaps in the mid-front of the tank. I think they will prefer the sand bottom, for scavenging. I got my hands on some quartz sand which i am about to start washing - i think it will need lots! 

So how deep should I make the sand cap? I was thinking 1/4 of an inch?


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## Fields of Blue

Hello, Rusalka. My personal experience with the El Natural style of tank has been with only a gravel cap and my success has been great. 
You can see a video of my tank right here;





Best luck too you!


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## Rusalka

While I'm waiting for all my supplies to come in I have a 1 gallon test nano with 1/4 inch sand and 1 inch of cheap soil and echinodorus tenellus. I did absolutely nothing to the soil before submerging it - straight from the bag to the fish bowl, and it is getting lots of window light. There is quite a bit of sand in the soil itself and there is a very thin layer (1/4 cm) below the soil. So far nothing dramatic has happened - there are no tannis leaching into the water and the plants look the same as when I put them in 4 days ago - so we'll see.


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## Rusalka

So my 1 gallon test is not performing as well as I had expected. The plants have not grown at all and aren't seeming to take root as I had expected so I tested the parameters and all was well within the normal ranges. But the water stank!!!!!!!!!!!!! Really bad. Not like sulphur, I don't know how to describe it. Sort of like the test tube when I test for ammonia? Any ideas what this smell is? 

I change most of the water and my MTS seemed to perk up after - hopefully my plants do too! 
I definately don't want to use this particular soil/sand combo if it's going to smell like this!! Argh.


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## torpedobarb

If I had the chance to redo it.. I would go with sand.. I mixed sand with sms.. it works though


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## Rusalka

The stinkiness is gone, phewf! MTS are nowhere to be seen (burrowing, that is!). I rescued a tiger lotus from being choked out by some dwarf sag and put it in there too - hopefully it will make a comeback.


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