Sunday, January 18, 2009

Garden Journal: Fishy Dreams

One of the concepts in the Toolbox for Urban Sustainability is the constructed wetlands.

A constructed wetlands is just that: a complete wetlands ecosystem constructed artificially. They are most often seen as part of a waste water handling system, one that can be applied with a minimum of technology or used for grey water treatment or whatever.

They can also be used for high-density, low-impact fish farming, since the wetlands both provides some forage for the fish and manages the fish wastes, producing both fish and excess vegetation, useful for eating by humans or animals or as green material for composting.

Such a wetland can also function as a water feature, something I've wanted for a while but was fairly low down the priority list (and fairly expensive to set up and maintain, to boot).

However, the constructed wetlands changes the equation: it plugs into the larger sustainable system, is itself inherently sustainable, and provides another source of home-grown animal protein at very low cost given the appropriate fish.

So now I'm actively, but slowly, working toward this dream of a having a small constructed wetland acting as a water feature and fish production system at the same time.

I had already had the idea of having a water feature that was powered by some combination of wind, solar, and human power (powering the pump for a waterfall, that is). A small-scale constructed wetland does require constant pumping and aeration (to ensure sufficient oxygen for fish in tight quarters), so having it be partly solar and wind powered would add to the sustainability (it would have to be plugged into the grid for backup if nothing else).

I've researched fish and the ideal fish is some species of Tilapia, which is essentially the chicken and rabbit in one of the fish world: it eats almost anything, grows quickly, reproduces prolifically, and tastes good too (in the sense that it produces a very mild white fish like catfish or cod).

It turns out that one species of tilapia, O. mossambicca (Mozambique tilapia) is legal to stock in private ponds without the need for any sort of exotic species permit or aquaculture license. The main challenge will be to get some (other than the challenge of actually building the wetlands itself)--I can't find any place on the Web that is closer than 5 hours away that sells tilapia for pond stocking.

But I am excited that at least this one species of tilapia is allowed in Texas—they are the optimal aquaculture fish and I didn't really want to have a catfish tank (although that would work ok too).

So we'll see how it goes—my next challenge is to scrounge the containers I need to build the four tanks that make up the wetlands—as with the rest of this project, I want to spend as little as possible on this. 55 gallon food barrels would be ideal and I know they can be had if you just find the right restaurant to talk to. But there's no hurry. And you never know what might show up on freecycle or Craig's list....

We are also close to pulling the trigger on rabbits. We've determined that the feed cost is acceptable and we have some room to put some hutches that's out of the way. So next step is finding some cheap rabbit cages and knocking together a little shelter for them.

All in good time....



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