# Plenum/Wedge idea



## kempstep (Oct 5, 2011)

I want to imitate the Amano appearance in my new tank and have the substrate slant up 3-4 inches towards the back.

So, I'm thinking about cutting a piece of acrylic that will have about 6 support pieces spaced evenly across the width of the tank. The pieces would be glued together and sealed into the tank on all four sides (using aquarium safe silicone), to keep water out of the plenum area.

I know others have used styrofoam or tile to achieve a similar outcome, but I want to know if anyone has tried anything like this, or think it would/wouldn't work.

Here are some of the specifics:

Acrylic: 3/16"
Tank: approx 36"W x 20"H x 12"

Also, if you have any other comments like whether the substrate will slide down too much on that angle or anything, that would help too.

Thanks in advance.


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## totziens (Jun 28, 2008)

I personally think that it's easier to get a bag of small lava rocks. Put them in a net. Slot the lava rocks in a net before adding any soil to form the slope. This is also useful to let bacteria grow in the lava rocks and prevent landslide. The net is optional but very useful to separate the soil and the rocks if your decide to tear down the tank in the future. This is the technique used by some of the high ranking aquascapers I know to save cost by not having to buy too many bags of ADA Amazonia soil.

I have personally used plastic container to form a slope but I believe there is a disadvantage of limiting the growth of the plants. The plants will be harder to propagate as the roots are blocked by the container. Therefore I believe the first option above is better than your method or my container. 

Since you are using acrylic tank, you just have to be careful about the lava rocks scratching your tank. That's the reason I have never recommended anyone to use acrylic tank - it gets scratched too easily comparing with glass tank.


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## kempstep (Oct 5, 2011)

Thanks for the response totziens.

I thought that if your substrate was too deep (e.g. putting lots of rocks under more substrate), you would get a large pocket of anaerobic bacteria and/or get lots of toxic gas buidup. I'm sure someone will correct me if I'm wrong, but I thought that was the whole reason for a max of about 3 inch total of substrate. If I did the lava rocks underneath, I'd have 5-6 inches of substrate in the back, and I don't want to kill the system from the very start, so that's why I was thinking I wanted an sealed/inert space underneath.

BTW, totzeins, the tank is glass (Amen to your comments about not using acrylic tanks cuz' they scratch -been there done that), just thinking of using acrylic for this sealed air space underneath, since its a bit easier to work with.

Thanks


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## totziens (Jun 28, 2008)

Anaerobic bacteria and toxic gas build up have not been my concern so far. I am actually not aware of such issue especially toxic gas. The LFS that I frequent as well as some friends have been doing the way I describe for years and I have yet to hear any complaint. The difference is most of them use ADA Amazonia soil but I am into NPT (I have a tank with ADA soil too but that tank does not utilise lava rocks). Most of us tear down our tanks once every 2-3 years. I have a NPT set up for my mother-in-law using the lava rocks method and a plastic container method combination. The only major problems faced during initial set up was diatom attack followed by tap water issue (water pipe repair) wiping out almost all of the lemon tetras (otos and swordtails were not impacted). The tank is still relatively new though as it's less than 6 months old.

Let's wait for further comments from other people even though I am quite confident that it's not an issue.


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## Michael (Jul 20, 2010)

This is a very interesting issue. I have used ceramic tile under the soil and cap to create a slope without problems. But the usual advice is to avoid deep substrate in soil tanks. Some people have told me to simply add more gravel cap to create a slope, but this seems likely to cause anaeroic conditions.

I suspect that we really don't know for sure what the effects of substrate depth are, especially because the effects can vary so much depending on the type of soil and cap. I am eager to hear other people's experiences and thoughts on this.

Kempstep, your wedge may be difficult to keep completely water-tight over the long term, and may eventually fill with water. I'm not sure this would be a problem, since any circulation between the water inside the wedge and the water in the soil would be minimal.

Thanks for starting the discussion.


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## kempstep (Oct 5, 2011)

Michael, thanks for the response.

While we're at it, I've got a tile question or two. Do you have any advice about tile selection? Do you know of any advantages or disadvantages of using different types of tile (e.g. ceramic vs. porcelain, clay, etc), and whether its glazed or not, etc? I'm probably over thinking this...like I said, just don't want to do anything majorly wrong from the get-go.

Thanks


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## Michael (Jul 20, 2010)

You're welcome.

I suspect the type of tile makes very little difference. I used high-fired glazed ceramic tile made in Italy, just because we had pieces left over from a remodeling project.


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## kempstep (Oct 5, 2011)

So, looking over other threads helped me realize that compaction (like from deep sand or certain soils over time) is what often leads to anaerobic conditions -because anaerobic means without air. So, if this is correct, the lava rocks in some mesh or putting tiles underneath work fine because they don't facilitate compaction any more than if there was just soil and gravel.

Now to decide whether to use tile or lava rocks...

I like that I don't have to worry about the soil eventually falling through the mesh if I use tile. But then I'd have find some tile and break out the tile saw.

Hmm...decisions, decisions.


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## Michael (Jul 20, 2010)

Perhaps if you used a coarse mesh bag you could spread inert gravel over the bag and lava rocks, then put a soil cap over that. I did something similar (without the mesh bag) in a display tank I set up for a LFS. The main reason at the time was that I didn't have enough mineralized topsoil for the full depth, and the owner of the store really wanted a big slope in the tank.

That tank has been set up for about 6 weeks and is doing very well. I will watch it closely for anaerobic substrate problems and report.

Lava rocks, with or without the mesh bag, are much easier to work with than tile.


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## totziens (Jun 28, 2008)

Yes, I think lava rocks are easier to handle. Mesh bag, net or even lady's unwanted stocking can be used to place the lava rocks to keep your life even easier - landslide among the rocks will be impossible.


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## kempstep (Oct 5, 2011)

All right, so I think I'm convinced that lava rocks would be easiest (thanks for the tips and advice totziens and Michael).

So, now -do you know of a good source for said lava rocks?

I'm assuming we're talking bigger size than normal aquarium gravel, but obviously not too huge. So, if they sell the right size at Home Depot, Lowes, Walley-World, or any other national big box that you know of, that'd be very helpful 

Thanks again


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## Michael (Jul 20, 2010)

I don't know what part of the country you are in, but around Texas lava rock is sold as a decorative mulch in the landscape section of any Big Box.


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## totziens (Jun 28, 2008)

I don't know which country are you from. I could recommend you where to buy if you're from my area but I doubt we're from the same country  They're quite commonly sold in Malaysian LFS but you don't want the gigantic ones - some people break the big ones into small pieces though but I think it's a waste. The ones I use are around the range of 0.5 inches to 2 inches in diameter (I use inches by assuming you're from the U.S.).


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## kempstep (Oct 5, 2011)

Yes, totziens, correct assumption, I'm in the U.S., Colorado to be specific  I forget how much of an international community we have here: Malaysia, Texas, oh wait 

So anyway, I don't know how many home improvement or gardening places will have lava rocks any more, since its kinda getting to be winter here -we just got 5 inches of snow the other day...


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## totziens (Jun 28, 2008)

There are a lot of Americans here. Hope someone will come to your "rescue" soon. Theoretically, it should be easier for you to get hold of lava rocks because there are volcanoes in the U.S. In my country, we have to import them from Indonesia (not too difficult too since it's a neighbouring country).  Good luck with your search for lava rocks.


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