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Monday, February 21, 2011

Poor Man's Greenhouse (aka High Tunnel)

$50 Greenhouse at

One of my early rants focused on the fact that it gets cold up here in the continental US. And not everyone has a greenhouse.

But with the White House using hoop houses and the USDA running around helping folks construct high tunnels, I've been seeing a lot about how one might be able to do a greenhouse for far less than $$$. The idea is you bend PVC pipe between anchors at either edge of the area, then drape the hoops with 6 mil polyethylene. Done.

Some things to consider.

Structural Stability

Door Garden reports the structure sprang back to shape once the snow was removed. But there are various ideas for making the initial structure stronger.
  1. Go Gothic - there's a reason those northern barbarians didn't use the classic roman arch - because it was liable to fail under load (think snow). A pointy arch can do beautiful things. Check out the post Another snow day at

  2. Use metal conduit rather than PVC. Turns out a conduit bender can be had for less than $40, and metal conduit is about the same price as PVC. Check out the Chiot's Run post about Building Hoop Houses out of Electrical Conduit.

Size constraints
  • Tiny yard. I live in a townhome. The entire thing is only 20' wide and about as deep.

  • Covenants. I'm not allowed to build anything that is taller than the fence around my yard.

I'm thinking of using the metal conduit to achieve a slightly more complex shape that would give me enough space for two rows of aquaponic growbeds without being taller than 6 feet. Here are some initial sketches:

The tall, flat wall will be next to the northern side of my fenced area. For the 8' x 15' plan shown, the conduit, bender, and 6 mil sheeting will run me about $250 (prices at Home Depot as of 2/21/11). Add a door, some lumber, and chicken wire, and we're around $300. I'd do a CHOP2 configuration, so there will be ~200-250 gallons of water in the system even though the tank, itself, is only 150 gallons. The Rubbermaid growbeds are $130 for the 150 gallon tank and $70 for each 50 gallon growbed and sump tank, so those would run me $700. Total $1000.

But I'd have no cost for grow-lights and the electricity needed to run them. That'd be sweet.

Too bad I can't use tilapia outdoors. I'll have to figure out what fish could do OK outside. Goldfish always work - they're cheap and 'dirty,' perfect for aquaponics. But ornamental goldfish can be carcinogenic if they've ever been treated with Malachite Green, so we couldn't eat them. I'll give my buddy at the Virginia Department of Game and Inland Fisheries a holler and find out what he recommends.


  1. Replies
    1. I ended up succeeding with bluegill, minnows, and goldfish in the sump tank. I've gone two winters now (and the summers, including a crazy heat wave) and all three species did OK outside. I didn't even cover up my greenhouse this past year until mid-January, and everyone survived fine.

      Again, for random folks who browse to this page, I ended up getting tapped to write The Complete Idiot's Guide to Aquaponic Gardening for Penguin Book Group. The book is now available for purchase at It includes lots of DIY plans as well as everything I wished I could have found in a book back when I was starting out (which wasn't very long ago...). So far the reviews are good!

  2. There's a long list of "Virginia Fishes" at the DGIF website, but they don't explain which species would do well in what is essentially a small pond. There are four varieties of catfish listed, though.

  3. So I'm seeing that channel catfish look pretty ideal, almost as "good" as tilapia in that they are hardy and will eat just about anything (including commercial feed, oh lazy me). This 1973 article talks about raising 40 catfish in a 55 gallon drum, which encorages me. It also looks like I could get 5" - 7" channel cats from Cast Away Lakes for only $1 per fish.

  4. I like to eat catfish, so when I start my system they'll most likely be my primary staple.

  5. I worry about the winter temperatures, though. Even with the greenhouse, it'll get nippy up here in the DC area.