Potting soil in an aquatic set-up

Several months ago, I was looking to renovate my small planted tropical fish tank (U.S. 16 gal) and I came across an interesting method of maintaining a healthy, naturalistic, sustainable aquarium. It involves using plain potting soil as the majority of the substrate. I know that this isn't a tropical fish forum, but I don't see why the method I used wouldn't work for aquatic caudates. Later this summer I plan on setting up a newt enclosure using this same technique. I'll let y'all know how it goes.

First off, I put about 2 inches (maybe a little less) of organic potting soil I got from Wal-Mart in the bottom of the aquarium. You could even use dirt from your garden, but only if you do not use inorganic fertilizers and pesticides/herbicides. Over this I laid a layer (about 1.5 inches) of puffed clay and pea gravel. The puffed clay was more of an experiment. Its intended use is for potting aquatic plants for garden ponds. I got it at a local garden center. If you don't have it available, plain pea gravel works just fine. The whole purpose of the gravel is to hold the soil in place.

At this point I planted the plants, arranged the piece of wood, and added some larger decorative rocks. Note: there is no water in the aquarium yet. Make sure the roots of your plants extend into the soil layer.

Very slowly add water and take care to not disturb the soil layer. The water should be relatively clear if done correctly.

Lighting: I used two full spectrum, screw-in fluorescent bulbs in two small clamp lamps. The bulbs are 26 watts each. It is very important to use the full spectrum bulbs! Otherwise, your plants will dwindle away. Check the color temperature on the package. It should be 6500K (standard light bulbs are about 2700). I got my bulbs at Menard's for about $5 each. I have them on a timer (12 hours on and 12 off).

Filtration...well, this is the catch...there is no filter! I have a small pump to circulate the water, but no filtration is necessary. The live plants and naturally present bacteria are the true filter. My aquarium has been set-up for about 4 months now, and I have yet to change water, clean it (except for occasionally scrubbing the algae off the glass), or vacuum it. I just add water periodically.

Some things to keep in mind:
Lots of plants are needed to make this work. Mine grow like crazy. I have to cut hand fulls of pond weed out of my aquarium on a regular basis. All the plants use up the nutrients in the water and prevent an algae bloom.
During the first month or two, your aquarium will look really ugly. This is a living biological system, and it requires time to balance out. Algae will take over and your water will get cloudy and a little murky sometimes. Do not worry. This will all go away. Having some good algae eating fish helps. I used 2 Siamese algae eaters and 2 octocinclus catfish.
Once this is set-up, do not do anything to disturb the soil. There are lots of bacteria breaking down the wastes of the animals and the organic matter in the soil. They are good in the soil, but they could be toxic if released into the water column.

Pictures
The first picture is what the aquarium looked like the day I set it up. Some of the plants really took off, and others did not work out so well.
The next pictures are of what the aquarium looks like today. I recently cut out a lot of the plants, but I'm sure they will be back. There is also duckweed growing thickly on the surface. I have to net it out when it becomes too thick. Some of the plants have grown to the surface and bloomed above the water (sorry I don't have any flower pictures).
As you can see, I haven't really aquascaped the aquarium. I pretty much left it to its own devices. This give the aquarium a much more natural and wild feeling (at least I think so). Kind of like a chunk out of a tropical pond.

So that's it. I just thought those of you who like naturalistic set-ups might be interested. This method was originally thought up by Diana Walstad. She is an aquatic plant ecologist and wrote a book all about this (Ecology of the Planted Aquarium). I didn't follow her method exactly, but her method was the major inspiration.

Let me know what you think.

Here is my recipe for my popei tank. I am going to be keeping the tank terrestrial with a false bottom. The substrate will be planted with crypts, java fern, java moss, and probably vals. As the newts become aquatic I will be increasing the water in the tank.

I am going to use the following mixture in the tank:
play sand
organic top soil
vermiculite
ground coco husk
peat moss

After this mixture is down, I may cap with a 1/2'' of play sand. I will be studying this mix and its moisture and drainage abilities as use in my PDF terraniums. The only thing that concerns me with my mixture is the peat moss. I am hoping when it goes aquatic it will not push the pH. I should have the mixture in the tank in about a week or so. My best guess is the popei won't go aquatic till March or April at the earliest and the peat moss will have settled down.

I think this is a cool idea. I really think that good old dirt is often "cleaner" than what people get when they try to maintain some sort of "clean" setup. It fosters the growth of beneficial bacteria and micro-organisms.

However, I can imagine some possible problems. "Potting soil" is a very general term, and different manufacturers put various things into their soil. The problems I imagine would be from using a potting soil that contains too much fertilizer, or one that contains those dreaded little styrofoam balls. Also, if someone used a layer of soil that was too thick, it could end up being very anaerobic (swampy/sulfury) down there. So... I think this is great, and could create a good environment for newts, but I worry about people jumping into a project like this and ending up with a disaster.

You're absolutely right, Jennewt. Too much soil will cause sulfur dioxide to build up, and that will be a stinky mess. I should have also pointed out that the soil I used had no added fertilizer. Provided that your backyard soil is safe, it would probably be better to use than bagged stuff. Also, the first fish I put in the tank were feeder guppies. They are cheap and hardy. After the water reached a balance, I was able to add more delicate species such as small tetras. From the very beginning I checked the water quality twice a day to keep track of what was happening in my aquarium.

This was definitely an experimental aquarium that just happened to work out for me. If somebody decides to try it on their own, I suggest doing a lot more research than just reading my brief thread on the topic.

Thanks for the feedback!

Asa,

That's very interesting and gives much food (without fertilizer of course) for thought. I have a fish setup with Eco-complete underneath gravel. The fish are fine but most of my plants except for the very hardy annubia, did not thrive, but the algae has. Whenever, I decide to break it down and rebuild, I think I'll try out your idea. Thanks again.

I have an aquarium with eco complete and have had nothing except success. I am confused why you would put gravel over the eco complete....Gravel is a detritus trap. I put in eco complete and added plants the next day. Plants have grown really well. My purpose in trying new alternatives is I hate spending $20 a bag for substrate, plus whatever shipping fee there is.

Before you blame the Eco what is your aquarium size, livestock bio load, plant load, ferts, lighting, level of expertise, etc...There are many other factors that could have led to your plants dying. Honestly the last place I would look is the Eco unless you are counting the gravel you put on top....JMO. Send me a pm if you wish to discuss further....

I am a fan of your method for aquaria, and of the Walstad book. I have done variations on this for a long time. Some have turned out better than others. As you say, rapid plant growth is essential. If the plants aren't growing, something is wrong. I start over then. I think nitrogen testing (ammonia/nitrite/nitrate) is needed at least until you are very confident that everything is working. I'm not a purist. I'll add a sponge filter. I'll also do some partial water changes. You might take a look at this thread which deals with denitrification:

http://www.caudata.org/forum/showthread.php?t=62251&highlight=denitrification

-Steve Morse

I am curious as to what the water chemistry test results look like for this tank now that it is grown in?

I often used a similar build when I bred soft water tropical fish. I suspect your method is much more stable than mine was.

At the time of the photo, the nitrites and nitrates by(API?) test strips were indistinguishable from distilled water. I've since moved the tank from PA to MN, changed the water, and haven't tested yet. I probably won't be posting here very regularly for a while as I've participating in various iron pours and living in tents w/o internet access. I will try to check in now and then. I have a few more details on the tank in the denitrification thread cited above.

-Steve Morse