# Substrate Depth



## Geomancer (Aug 23, 2010)

So what is everyone's thoughts on maximum substrate depth?

How would you go about achieving a deep substrate?

I'm in the process of planning out an aquascape in a large aquarium, so I have room to work with. I'd like a raised section, where the substrate would be in the order of 4-6 inches in depth. The substrate will either be a sand, or small gravel (~1-2 mm in size).

I know you can run into gas problems with a deep substrate... so I have a couple ideas.

One is to have Malaysian Trumpet Snails, I'll have these guys regardless but I hear they help (but to what extend?)

The second is maybe using a layer of larger gravel (small rocks) to form a base, then cover with the fine gravel/sand. I'm aware the fine stuff would filter down into the rocks, but should still keep them covered (say 1-2" of stones and 3-4" of sand/fine gravel on top). Think this would work? Or long term would the larger rocks/gravel somehow 'float' up to the top?

I should add the tank will be heavily planted with live plants.


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## CinBos (Feb 23, 2012)

Geomancer said:


> So what is everyone's thoughts on maximum substrate depth?
> 
> How would you go about achieving a deep substrate?
> 
> ...


Good question. I was thinking the same thing, but more along the lines of, how deep or how shallow can you have substrate?


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## Byron (Mar 7, 2009)

Mixing substrates is not a good idea, for the very reason you mention. Gravity and water movement (water must move through the substrate, and if the tank is biologically balanced it will) will eventually have the sand on the bottom and the gravel on the top.

To the depth, less is better than more. I would not go over 3-4 inches at the deepest point, namely in back areas where plants with extensive root systems like the larger swords would be. Down to 1 inch along the front is fine. As the substrate will shift to even out (same reasons as above), terraces made from rock or perhaps wood will be needed to keep the differing levels.

Anaerobic areas are actually wanted, they are part of the complete biological balance of a n aquarium; but we don't want them taking over the substrate. Plant roots do a lot to prevent this, as do the Malaysian Livebearing snails. [In marine systems there are types of worms that work the same.] There is a bit more info on this aspect here:
http://www.tropicalfishkeeping.com/freshwater-articles/bacteria-freshwater-aquarium-74891/

I now have playsand in 4 tanks, the largest is my 5-foot 115g. The total overall depth was about 2 inches, and I pushed some areas deeper with flat basalt rock for the larger swords, though in the past several months it has, as I mentioned above, evened out a bit. But the plants are established so they manage. I don't touch the substrate, by which I mean no vacuuming, poking, etc. The plants and snails take care of this. Some anaerobic areas do exist, but I've never had hydrogen sulfide problems. I recently did some re-arranging in my 33g that has been setup with sand for over a year, and even in there with 1.5 inches sand I didn't detect issues. Some pretty black areas, but the fish weren't bothered.

Byron.


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## Geomancer (Aug 23, 2010)

Can you explain more on how to use rocks for a terrace?

I was envisioning putting down ~1.5 inches of sand/gravel (technically I believe the term is Very Coarse Sand for 1-2 mm). Then say a horseshoe made of larger rocks butting up against the back glass, and then filling the inside of the horseshoe with more sand/gravel to get a higher level.

Basically, I would want two levels that each would have rooted plants.


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## redchigh (Jan 20, 2010)

If you really want a 'shelf', then I would just carve some styrofoam the shape of the shelf (make sure the top is not smooth- the rougher the better), paint with Krylon Fusion in Black.
(I've used it a million times to paint decorations... Just let it dry for a week.)

Then glue it to the bottom of the tank with aquarium silicon.

Let the silicon dry for however long the instructions say, then cover with gravel. Slate would also work...


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## Byron (Mar 7, 2009)

Redchigh has probably the best method. If you use rocks, get fairly flat slab type, but thicker than shale (too thin). I have basalt chunks I got from the local stone supply, it is inert. They are heavy, each chunk is about 1.5 to 2 inches thick. Sometimes you can find chunks that sort of "fit together" to create a low wall. Silicone them ensures a better fit, as the sand or gravel will work its way through the smallest crack. If the rocks sit on the tank bottom glass, and not on sand or gravel, they will hold better; silicone again helps with this.


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## Geomancer (Aug 23, 2010)

Would I need some kind of a lip to contain the sand? The large retaining rocks won't fit perfectly up against either flat rock or styrofoam, would relatively small sections at depths of ~4-5 inches not be too bad?

I'm also guessing that in my large rock retaining wall I would have to 'fill the gaps' with silicone? Maybe actual small gravel would be better on the terraces, while keeping the coarse sand on the lower level.


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## redchigh (Jan 20, 2010)

look up how to make paludariums... They have work arounds for deep substrates.


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## Egrant (Dec 2, 2010)

Redchigh, 
What kind of glue to use? I was goign to make some decorations but want to make sure it safe.


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## redchigh (Jan 20, 2010)

aquarium silicone is best.
superglue can work, but use the silicone.


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