Construction Begins, Wicking Philosophical– Glorious Hindsight

Excavation for the fish tank's reinforced concrete slab base

That’s a haiku, by the way. For those of you who read my last article, you will notice that the aquaponic system has found a new location despite having had the legendary Kubota tractor level a site for it elsewhere. The story of how this came to be will be the topic of my next article. A word of caution, though: it will be an excruciatingly painful read. . . This article, however, is all about optimism, optimism, optimism. And, although I had to leave the site before it was completed, there is an 8,000 liter fish tank in the spot shown on the left. That’s progress!

This is the uppermost tier at the entrance to the land

The new location is the already-level uppermost tier of my 3-tiered land. It’s so bloody obvious as the most suitable site that it remained almost entirely hidden by my big, Western nose. It’s at roughly the same level as the main road. I have to sacrifice some coffee trees, however, but I was assured that they weren’t very productive in the first place. There’s plenty of room, too, enough for at least two, perhaps three aquaponic systems. Speaking of aquaponic systems, mine has evolved quite nicely. It is now integrated “symbiotically” with wicking beds and, of course, upside down tomatoes– I’ve got to live up the the “Wrong Way” name.

System Overview

At last, a system that I'm satisfied with-- and just in time, too.

The aquaponic component is pretty simple, and I’ve gone on at length about how it works before, but here is a reminder. The fish in the tank are fed. Initially, I’ll use commercial, high-quality fish feed, but eventually I’ll transition this to a combination of worms and other sources produced on site. The water is recirculated. In fact, the fish tank water should be cycled about 18 times a day. The water from the fish tank, along with the fish poo, uneaten feed, and other waste products such as ammonia pass first through the the larger blue barrels. These are known as swirl filters. The heavier solids swirl down to the bottom of the barrels where they are removed, probably a few times a day. What’s left is water with the finer solids still suspended. This stuff passes through the first of the smaller barrels. After a lot of thought, I’ve decided to use a mixture of coir (coconut husk fiber) and rice husks in a 70:30 ratio. This mixture will be wrapped in mosquito netting like a giant teabag. Two things happen here: first, the suspended solids are trapped in coir fibers, and second, the immense surface area is home to the bacteria that convert the otherwise noxious stuff to plant food. The bacteria have other homes, too; in fact, every surface, including the underside of the Styrofoam rafts. It’s this suspended solids media that I’m particularly satisfied with (if it works). First of all, the rice husks are free, and if I can’t get coir for free, it won’t be expensive. But the great thing is that it’s all organic. Coir is rapidly replacing peat moss as the main ingredient in soiless potting mixtures. So, instead of using orchard netting as the filter media, which would have to be rinsed periodically, I can just replace it with more coir and rice husks. And what do I do with the gooey stuff? It goes to the wicking beds, of course. Let me just say that wicking beds are tremendously sexy. More about them later. The final barrels are just a “degassing” zone. Significant aeration removes methane and other nasty stuff from the water. They will also serve as a vehicle for tweaking the PH of the system water when necessary by adding hydrated lime, etc.

Aquaponic Component

While wicking worm and potato beds are a new component in the overall system, the aquaponic component has gone through some nice evolution. The greenhouse length is now more than 2 meters shorter yet maintains roughly the same level of production. There are 3 longer hydroponic troughs instead of the 4 shorter ones, allowing me to eliminate one set of filtering/degassing contraptions. The system details are as follows:

  • Fish tank water volume: 8,000 liters
  • Annual fish production: 1 to 1.25 tons
  • Hydroponic trough water volume: 16,200 liters
  • Annual lettuce production @ 3 weeks on rafts: 15,600 heads
  • Freshwater prawn production in the hydroponic troughs: not sure

 Wicking Beds

Lateral drift is my best friend. The world is, luckily, full of lots of clever people. I’m not going to bore you with the science behind wicking beds; if you want more information, try reading this. From the same source, “The wicking bed system is a way of growing plants in which water wicks up from an underground water reservoir. The major advantage is a significant increase in production while water use has been shown to be reduced by up to 50% of conventional practice.”

Step 1: Wrong Way Wicking Bed

Here is how I’m intending to make my wicking beds for potato production. I will discuss potatoes at length in a later article. First, dig the reservoir pit. This is about 20cm deep. The reservoir should not be deeper than the capacity for water to wick, which depends on the wicking media, but coir can do about 30cm. Next, line it with leftover greenhouse plastic. Then put down the perforated wicking pipes. These are just fairly large diameter PVC pipes with lots of holes drilled into the sides. They are about 20cm long, too. Then lay the irrigation pipe. This can be perforated or just slotted along the bottom. The inspection/refill bit allows you to check the level of the water in the reservoir. A normal wicking bed would just use boards or something for sides, but I’m going to use old tires because I hope to get them free and worms cannot escape easily (I dare them to try!).

Step 2: Wrong Way Wicking Bed

The pit then gets filled in. I’ll probably use river gravel because it is roundish and facilitates a large volume of water. The whole reservoir then gets a layer of shade cloth. This is to keep the grow media in the tires separated from the reservoir. It has to be pushed into the wicking pipes to allow the coir-based media to get down to the bottom of the reservoir. I think this is fairly clever, but I welcome any suggestions. Other wicking beds that I’ve seen just have a corner or two of the reservoir devoid of gravel so the wicking material can be fully immersed in the reservoir’s water.

Step 3: Wrong Way Wicking Bed

The tires can now be placed on the wicking bed with the wicking pipes at their centers. As the potato plants grow, more tires are placed on top and grow media added. Potatoes are cool; the right ones will just keep producing potatoes at higher and higher levels, to a certain degree. When the stack reaches about 3 layers and the plant decides that things are going tits up, just kick over the lot and separate the potatoes from the worms and grow media and start again. I could use water from the aquaponic system, but I probably won’t have to. With worms continuously feeding on the fish poo and producing castings, there will probably be enough nutrients in the media to support a crop to maturity. Carrots, radishes, and other such things can be grown this way, of course.

Upside Down Tomatoes

I've just got to do this. Wrong Way tomatoes!

This is a subject that caught my attention some time ago and was put into one of those dusty compartments in my brain. I was looking for information about growing things in micro-climates similar to the Bolaven Plateau. The Olympic Peninsula in Washington is one such place. Cool with lots of rain and little sunshine. There is a lot of debate about whether tomatoes (or bell peppers, for that matter) grow better this way. But there are certainly advantages. These include better air circulation, inaccessibility to creepy crawly things, and the use of vertical “dead space.” This photo is from an article about a guy named Dick Schneider. It makes for very interesting reading. I’ve emailed the publisher of this article as I’d love to get in touch with this fellow. Notice how he uses black pails. This heats up the media a bit which is good for tomatoes. A disadvantage is that the growing media dries out quickly. It’s also heavy, if ordinary soil is used, but I think my soiless grow media will be okay. I look forward to experimenting.

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2 Responses to Construction Begins, Wicking Philosophical– Glorious Hindsight

  1. Michael Sandeman says:

    Where’s the kigo?

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