# How to terrace a soil-based tank?



## littleguy (Jan 6, 2005)

So I'm almost ready to set up my 40 gallon breeder, and was thinking about terracing or sloping the substrate for aesthetic reasons, much like is done in many of the higher-tech tanks. The tank is 18" wide (front to back) and I'm thinking about having the substrate be 2-3" deeper in the back than in the front. For example, having 2" depth at the front (1" soil + 1" gravel) and having 4-5" depth at back.

I'm wondering how best one might do this with a soil based tank. I understand deep substrates can be problematic with going anaerobic, H2S production, etc. To me, the obvious (but not necessarily acceptable) solutions are:
Maintain 1" soil underlayer throughout. Then cap with gravel that goes from 1" thick to 3.5" thick.
Slope both the soil underlayer and the gravel cap. Soil goes from 1" thick to 2" thick; gravel goes from 1" thick to 2.5" thick.
Use large flat rocks to build up a terrace underneath the soil. Then cover with ~1" soil, then cap with 1.5" gravel.










Option 3 seems to be the safe way to go. I'm guessing that options 1 and 2 would likely have problems with anaerobic zones, with such deep substrate.

What do you think? Can anyone see any problems with option 3? Has anyone ever had success with options 1 or 2? Does anyone have any other ideas/experience?

Thanks!


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## bpimm (Jun 12, 2006)

Option three is the best option listed, the other thing I have thought about is to use sand to slope the bottom so you can maintain the soil and gravel later thickness. if you were to use a sand that compacts well it may not have a problem with going anaerobic. Just a thought, I haven't tried it wet.  

Maybe a combination of both, use the rocks with sand around them so you don't have the deep soil pockets in between the rocks.

Brian


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## littleguy (Jan 6, 2005)

Hmmm... yeah I was wondering about sand too... although usually it seems to get the :thumbsdow for Walstad-style tanks.

I wonder how a person can determine "good sand" vs. "bad sand" for this application?

Thanks,


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## dymndgyrl (Jan 22, 2007)

Even with the rocks you will have anerobic pockets. Also, I suspect the substrate will shift over time and even out leaving the rocks exposed. The only way around that would be a wall or shelf of exposed rock or something that holds back the upper level.

Here's a link to the Dutch method of aquascaping that talks about terracing:

Aqua Botanic - Secrets To Dutch Aquascaping

But if this is going to be a NPT and therefore heavily planted, you are probably going to lose sight anything decorative about the substrate anyway -Why not just create a layered look with plants - taller in the back, shorter in the front etc . . .


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## littleguy (Jan 6, 2005)

dymndgyrl said:


> Also, I suspect the substrate will shift over time and even out leaving the rocks exposed.


Yeah, you may be right. That would be no good at all!!

In terms of plant layering, yes, that's definitely the fallback plan. I'm not dead set on terraced substrate; it's just something I'm bouncing around in my head. I'm kind of inspired by some scapes with sculpted terrain, for example

2005 AGA Aquascaping Contest
2005 AGA Aquascaping Contest

But then again, even these tanks show how a similar terraced effect can be achieved by careful selection of plants.

Thanks!


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## sb483 (May 29, 2006)

What about option 1 with more soil & less gravel and vigorous plants like red tiger lily in the deep end?


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## AaronT (Apr 26, 2004)

Option 3 would use more soil than necessary and cause anaerobic pockets in the substrate. Over time option 3 would settle out to look like option 1, only you'll have used more soil and have too deep of a layer. The soil is extremely fine and will settle evenly over time.

My advice would be to go with option 1 and plant heavily from the start. This will ensure that any possible pockets are filled up with nice healthy roots keeping the substarte aerobic and healthy.


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## littleguy (Jan 6, 2005)

AaronT said:


> ...Over time option 3 would settle out to look like option 1, only you'll have used more soil and have too deep of a layer....
> My advice would be to go with option 1 and plant heavily from the start....


Good point too. Maybe I need to rethink this... looks like all three options have risks. I'm not sure I want to gamble with the foundation of the whole ecosystem.

Thanks for all the great input so far. Keep the ideas rolling if you have any more!


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## AaronT (Apr 26, 2004)

If it makes you feel better I've actually used option 1 three times with good success.


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## littleguy (Jan 6, 2005)

Another concern with option 3 that just occurred to me is that the rocks might act as pressure points on the bottom glass and crack it if I'm not really careful.

Which leads me to *option 4* - using something soft and inert instead of rocks. Like a big wedge of styrofoam under the soil, sculpted with a nice grade. Although I'm not sure how safe it would be in perpetual contact with water, soil, bacteria, roots, etc. But it would avoid having soil "fall between the cracks" like would happen with the rocks. Just another thought.


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## littleguy (Jan 6, 2005)

AaronT said:


> If it makes you feel better I've actually used option 1 three times with good success.


Cool! Could you give specifics on soil depth and gravel depth? Thanks!


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## AaronT (Apr 26, 2004)

littleguy said:


> Cool! Could you give specifics on soil depth and gravel depth? Thanks!


Sure thing. I used about a 3/4" soil depth. I topped it with 3M colorquartz sand, about 1" in the front and 2 1/2" in the back. Those measurements are in addition to the soil depth.

I think you might still run into a settling issue with option 4. I use the 3M sand because it's still nice and coarse and it's very dense so it holds a nice slope for a longer period of time. The soil underneath will level out over time because it is so extremely fine. Here's a visual I worked up.


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## littleguy (Jan 6, 2005)

Awesome. Nice visual. Yeah, I thought you might say that.

Thanks much for the detailed specs, that really helps.

Another good thing about option 1 is that it seems you could regrade the gravel back to shape if you ever had to, without disturbing the soil.


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## AaronT (Apr 26, 2004)

littleguy said:


> Awesome. Nice visual. Yeah, I thought you might say that.
> 
> Thanks much for the detailed specs, that really helps.
> 
> Another good thing about option 1 is that it seems you could regrade the gravel back to shape if you ever had to, without disturbing the soil.


Exactly.  At some point regrading will become necessary. The soil should last for years and years so it'd be a shame to have to keep redoing things every time.

Where abouts in VA are you located? If you don't want to say specifically here you could PM me. I ask because we have a lot of NOVA people in our local club and it would be cool if you could make it out sometime.


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## Robert Hudson (Feb 5, 2004)

Over the years of trying several times, I found that when ever you build retaining walls of some kind of gravel, sand, or loose rock, it always settles and levels off eventually. Everytime you plant or remove a plant you only excellerate the process.

A wall that will hold the substrate without leakage or movement is fairly easy to do and there are different ways to go about it.

One time I made a rock wall by siliconing rocks together, and filling the gaps with gravel on silicone.



















In this case what I did not like about it was the rocks I think ended up being too big for the look I wanted, and it did not leave as much room on the terrace for planting as I would like.

Another alternative is to use walls or partitions made of plastic, aryllic, or styrofoam. These can be thin, take up less room than rocks or wood, and be less obtrusive. If you use clear plastic, you can create the illusion of a steep slope without the partition being obvious.You have a plate on the bottom of the aquarium with the partitions attached to it. You can glue them or silicone them to the plate, or if you are more creative, you can make grooves for the partitions to fit in or some type of screw or dowel holding them upright.

The most effective terrace is the most secure terrace that will not move, drift, fall down. Loosely placed or stacked wood will most likely at some point become ineffective or diminished. With firmly afixed partitions, you can re arrange plants, or even change the substrate from the created compartments without having to rebuild the terraces. It is almost like creating pots for the plants to grow in. This way you could even have different substrate material in various compartments, or replenish the soil one compartment at a time.

There might be a plastics store in your area that will cut sheets, strips to order for you. I used to go to a place called Tap Plastics. Home Depot will cut sheets for you. All you would need to know is the measurments.

Whatever way you do it, build the terraces before adding any soil or gravel.


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## littleguy (Jan 6, 2005)

Wow Robert, great info and pics! You answered questions I didn't even know I had . This has been a super helpful discussion - a day ago I might have been on my merry way with rocks under the soil - only to have an assortment of settling and shifting problems degrade my handiwork weeks or months later. Your collective years of experience have saved me a lot of anguish.

So I'm starting to conclude a couple things:
If a person wants relatively mild gradation of the substrate (an inch or two rise over the span of a foot) then Aaron's method (aka "option 1") will probably work just fine (assuming healthy planting), plus has the benefits of easy setup/maintenance, and some flexibility for reshaping if your needs change later.
However, if you need more severe grading/terracing, then the best long-term solution would involve pre-fabricating some underground retaining walls as Robert describes. Without the retaining walls, everything will eventually degrade into a more or less level field. The retaining walls also let you compartmentalize plants and possibly different soil types, which could provide some interesting scaping options.
Thanks for such great responses! I'm going to have to let this simmer while my aquascaping vision starts to come into focus.


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## Robert Hudson (Feb 5, 2004)

I have another idea that I havn't tried yet, so I don't know how well it would work, but I think it would be cool to use a partition that was flexible: that you could bend. Then you could bend it, curve it to your liking instead of being restricted to a straight line. I actually have a new tank that I am setting up, so I am going to try something like this. I have been going over and over it in my head as well, so we are in the same boat!


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## treesmcdonald (Mar 14, 2006)

I'm not sure how valid this suggestion is. But I have seen people build up grades in terrariums with those little clay balls used in hydroponic set ups. They are very porous so they probably wouldn't become anaerobic like rocks or sand. I'm sure the really fun part would be getting them to stay in place. They would probably only good for a mild grade. Like Aaron I just went with option one in my tank and I haven't had any problems yet. Knock on wood.


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