Monday, July 15, 2013

Aquaponics Design

When Matt and Elise introduced us to aquaponic farming, we thought, 'How cool!  We like to eat salads and fish, too!'  and we knew we were going to have to try it.  The trick was, we didn't have the space for a big greenhouse and grow beds.  To make matters worse, we didn't even live on the first floor of our building, which meant we were fairly restricted in how large a system we could build.  A third strike was that at least 50% of our household (population: 2) didn't want some cobbled-together monstrosity in the guest bedroom.  It had to look nice.  But with a little old-fashioned creativity and some elbow grease, almost anything is possible.

In the interest of full disclosure, we didn't have the foresight to take a lot of photos while we were building the system.  But now that we have a blog to post this kind of stuff to, we take pictures of just about everything.  Since we're packing up to move soon, that means temporarily deconstructing the aquaponic system...and a second chance to record the construction process, albeit in reverse.  The bonus for you, faithful readers, is that we can reflect on the system's form and function over the last year or so, and you can avoid any mistakes we made the first time around (there might have been one or two).  The deconstruction is currently underway, but of course, it needs to be essentially complete to start the story at the beginning.  So for today, we just wanted to give a quick overview of our design and what went into our thought process in figuring out the size, location, and orientation of the system.  And to make some fun pictures in powerpoint.

This is a schematic of the system.  It's not quite to scale.  You can tell because we had more than one fish, and they were all much smaller than the one shown in the tank.  Also, the plants were much bigger.
One of our primary concerns in setting up the system was the weight.  We've got the weight of the water, the grow bed, and the wood frame as the major factors (and, in our imaginations, the weight of the fish).  We read that tanks up to 55 gallons can go just about anywhere.  But what about a 50 gallon tank attached to a 50 gallon grow bed?  We might be pushing the limits a little bit there.  In order to spread the weight out as much as possible, we decided to go with an L-shape, with the grow bed overlapping the tank.  In our particular situation, the floor joists are perpendicular to the long side of the grow bed (we think), so at its heaviest (grow bed full of water), the load is distributed across more joists.  Along the same lines, we went with Hydroton as the growth medium since it is considerably lighter per volume than gravel or sand.  (The tradeoff is that it's relatively expensive, but we were lucky enough to find a local place that was selling it for almost half off the cheapest online source we could find!)

We found a fish tank on Craiglist without much trouble, but the grow bed took a little more thought.  We had settled on a wood frame, but we needed to line it with something waterproof.  We considered a variety of totes and other containers, but in the end we decided on an EPDM rubber pond liner for its durability and fish safeness.  We searched a number of places online, but the best value seemed to be Just Liners. (It must be one of those ironic names, since they clearly sell more than pond liners.  Or maybe their liners are socially responsible.  We may never know for sure.)  We were happy with the purchase, and haven't had any leaks.

Part of the reason the liner has held up well might be because we were careful not to let any sharp corners or edges rub against it.  Before we set the liner in place, we padded the inside of the wood frame with wood shavings (we had a lot because we got the frame lumber rough-sawn and planed it in our living room with a little 10" power planer that we also found on Craigslist.  (That's a good reminder--we probably owe our neighbors another plate of cookies.)  The wood shavings also gave us a chance to form the bottom so that the lowest part was the area by the siphon, and minimize the amount of water that stayed in the grow bed when the draining stopped.

One advantage of having the orientation set up this way is that the only breaks in the grow bed liner were directly over the fish tank, where we had to punch through to install the siphon and overflow pipes.  Thus, any leaks were likely to cause minimal damage.  The tradeoff is that the back half of the fish tank is not very accessible.  (Guess where the fish preferred to hang out?)  It was difficult to check in on the fish, and sometimes even find them, because the grow bed blocked both view and access.  In the next system we build, we will try to create less of an overlap.  As a side note, minimizing overlap was one of the design principles Sylvia Bernstein recommended in her Aquaponic Gardening book (which we ignored, and now wish we hadn't).

This is one of the few photos of the young system.  It shows the general location of the system (with which we tried to maximize the natural light contribution), and the grow bed before it was completely full of Hydroton and had its pond liner was trimmed.  It also shows the lighting setup, which we'll cover in more detail in a future post.

For the plumbing between the pump and the grow bed, we used clear vinyl tubing.  It has worked well, with a few catches.  Having clear tubing is disadvantageous because algae will grow on the inside of the tubing.  It's inevitable.  At first, the algae would build up to the point where they started to block flow, and the siphon wouldn't trip to drain the grow bed.  Then we had to try to clean out the tube, which worked best if we threaded a piece of fishing line through it, wrapped a small piece of cloth around one end, and pulled it through the tube like a miniature cylindrical squeegee.  The first time, it took almost an hour to thread the fishing line through the tube (with the help of several skinny, heavy objects), but then we left the fishing line in there, with enough out one end to pull our little squeegee through and not reach the end of the line.  That saved us a lot of time for the second pass.  Still better was when we got smart and buried the tubing in the Hydroton except for the very end.  Then the algae didn't build up at all!  Additionally, the flexibility of the tubing is nice to have, especially for water changes.  It's much easier to alter the configuration than it would be with the rigid PVC piping normally recommended.

Finally, having the storage space underneath the grow bed has been really nice.  It has allowed us to keep all the aquaponics equipment in one place, and out of sight.  Spare pumps, leftover pond liner, the carbon filter for chlorine removal from the water, and fish food all stay there.

In sum, we have been happy with most of the features of this design, except the overlap of the grow bed and fish tank.  It looks nice enough to keep Katie happy, and produces enough basil to keep Jake happy.  Check back on Thursday for more details!

Have you tried your hand at aquaponics design?  Have you had to consider weight restrictions in locating a fish tank?  Tell us about it in the comments section below!

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