As promised, here are the work-in-progress shots from the fish tank. Each photo will have a description above it.
I had a number of pieces of driftwood to choose from and arrange. I opted to go for a slightly off-center stellate arrangement. The lighter piece in the front eventually got moved out of the tank, which you’ll see later. With that arrangement documented, I took some of the pieces out so I could get started with the substrate.
When you’re building a tank, you have a TON of options for how to put it together. I’m 100% adamant about using live plants, which limits the kind of gravel/substrate I can use as well as the type of fish I can house. In my smaller tank, I used a specialized pulverized volcanic rock that is great for holding nutrients and letting plant roots grow. It’s quite costly, so I researched different options.
I settled on a pathway called a dirt tank. This approach was described by Diana Walstad in her book Ecology of the Planted Aquarium. In this type of tank, actual soil from outdoors is used as the bottom layer in the aquarium. It’s capped in sand or another type of gravel to prevent it from heavily clouding the water. This method allows the plants to be fertilized by the decomposing dirt and all of its many chemical and biological processes. The nice part about going along with “nature’s recipe” is that it’s very inexpensive.
There are some special rules, though. The dirt can’t be too deep or it will develop anaerobic (no-oxygen) layers, which can release toxic chemicals and gases into the tank. The sand on top also can’t be more than about 1.5″ deep for the same reason.
Good aquarium design (referred to as aquascaping) has a few guidelines of its own. One is that you want the substrate to have some contours in it. You also tend to want to have the back of the tank to have the substrate rise up in a slope. It helps with visibility. These rules presented a problem, though. If I piled up dirt in the back, it would be well over the 1.5-2″ depth of soil and sand that I wanted.
I solved that problem by creating a terrace system with paver bricks. Between the pavers and back wall of the tank, I used some very large landscaping gravel (sand gravel) to fill in the space. This layer-cake approach would allow me to slope up the back of the tank without getting anaerobic areas in the soil layer. I was also able to create a few small plateaus around the base of the driftwood. That will allow me to get plants in at different heights, which adds depth to the aquarium when viewed from the front.
Next I had to create a buffer between the front of the tank and the rest of the substrate. This is another nitpicky choice on my part. If you layer your substrate, you’ll see the layers at the front of the tank. I didn’t want that, so I placed cardboard, behind which is another barrier of those pavers on-end. It gave me a buffer of about 1.25″ at the front and sides of the tank.
On the very bottom of the tank, I put down just enough of the fancy plant growing gravel to cover the bottom glass of the tank. I also poured some on top of the sand gravel so that the dirt layer wouldn’t just flow down into it. I used a mix of FloraMax and EcoComplete since I had some left over from building my other tanks.
The next step was to build up the contours throughout the tank. When dirt and sand get wet, they don’t tend to hold a slope particularly well. The fancy gravel does, but I didn’t want to use too much of that. After some additional research, I found that many aquarists have used a special kind of fluorescent light cover to do the trick. It’s basically a plastic grid. I cut pieces into the sizes I needed and placed them in the tank where I wanted the slope to be. Here you can see the black plant gravel on the bottom layer.
The dirt went in next. On top of that, I poured some more of that fancy plant gravel. I did this mainly to give the soil a material that would hold nutrients and slowly release them over time. This substrate is also very porous, which allows LOTS of bacteria to form. The bacteria are what will break down the soil and release useful chemicals for the plants. You can also see that with the help of that plastic grid, the substrates are holding a very nice slope.
The last step with the substrate was to place the sand on top. This layer allows for some more creative aquascaping. I attempted to put in some elevation changes to reflect ripples or a sandbar sort of layout. I’ll come back to comment on how well that worked out in a bit.
Once the main area of the tank was capped in sand, I carefully lifted the border of pavers out and filled the perimeter with sand. This worked out just about perfectly. I have a few spots about 0.5″ in diameter that didn’t fill perfectly. I’m comfortable with that. I can probably fix them after the tank is filled and everything has settled for a while.
Once the sand was placed, I bought some river rocks to scatter. I have a mix of sizes, and eventually I’ll place some gravel on top of the sand in a few spots as well. I very carefully put some dechlorinated water into the tank to begin wetting down the dirt and sand. I was also hoping that the driftwood would soak up some water.
One of the methods that Walstad discusses in her book is the “Dry Start Method.” This means that you don’t fill the tank with water right away. You keep the bottom of the tank very wet for a bit. Then you plant your plants. They’re kept moist and given lots of light. The amount of CO2 in the air is higher than what dissolves in water. The plants grow like crazy, establishing good roots and strong stem growth. After a month or two, you flood your tank and all is well.
I’m not that patient. I wanted to do the dry start, but I couldn’t stand it. I know the tank will need a couple of months at minimum to go through all of its chemical changes before I can put living things in it. I’m eager to get that started as soon as possible.
On Sunday, I filled the tank. I’ve got a filter that’s technically too small for the size of the tank running just to get some of the beneficial bacteria to colonize. The heaters are in and I’ve got bricks holding down the driftwood so it can soak in water. Eventually, it won’t float anymore and I can remove the brick weights.
For now, I’m in a holding pattern. I’ll have my good, big filter in place in a few weeks. Then, the lighting, which will be a whole post by itself.
In the last few images here, I used a plastic bag to stop the water from disturbing the sand and rocks while I filled the tank. The careful contours that I laid out resettled into their own pattern, but I like what I’ve got so far. Time will tell if it stays nice. 🙂