We have finally finished construction on our aquaponic raft beds, also known as Deep Water Culture (DWC)! The system is up and running and we have hooked the raft tank in to the main fish tank, so the water is full of nutrients that drain from the grow bed and fish tank. We aerate the water with an air pump hooked up to air stones, and the plants’ roots hang down into the aerated water.
Even the children are excited, and got to help us transplant the first lettuces into the raft.
These beautiful red and green lettuce should be ready for market in 3-4 weeks.
When last we checked in with Mr. Greenhouse we were finishing up the structure, covering it with shade cloth, and outfitting the interior. That seems impossibly long ago, but it was only this past summer. Summer is long gone, and cold weather is here. There are two times when a greenhouse really comes in handy: keeping things cool in the summer under the shade, and keeping things warm in the winter.
Preparing for winter by removing the shade cloth and putting on plastic seemed easy enough—sure, we’ll just pull off the shadecloth, roll it up, and pull the plastic over. No problem! Ahem. It was a lot of work. Especially because the weather was preparing to change, and it had been windy for several days. We waited weeks for a calm day, and eventually decided to try it on a nice morning with just a hint of breeze. It was a beautiful day.
Getting the shadecloth off, truth be told, was a cinch. Just un-clip the sides and pull it off. The next job was to pull the plastic over. We bought a large roll of plastic, 55′ long and 44′ wide. It’s wide enough that the sides hang down to the ground to cover our tall windows. I tied a one end of rope to one corner of the plastic and the other end to a roll of duct tape, which I then tossed over the hoop frame.
We pulled and pulled, and inch by inch the plastic came up over the hoops. Amazingly we had no tears. We got it centered, and started securing the clamps along the side. That’s when the wind came up.
In spite of the wind (which was not much more than a breeze, but that much plastic acts like a sail on a sailboat), we managed to get the sides clipped down and secured. All was straight, tight, and beautiful with no tears or holes.
To attach the sides we used the Tube Lock base and clip that we procured from Greenhouse Megastore. On the ends walls we used the Spring Lock base and clip. After using both I can say I highly prefer the spring locks, and I won’t be using the tube locks again. The tube locks are very strong and look nice but they have a tendency to slice through the plastic if you put too much force on it. The spring locks will not harm the plastic and are extremely easy to install – just thread the spring lock into the channel of the base, and it holds everything very securely.
The sides are rolled up using a long pipe clipped on with fabric clips from FarmTek. We added a hand crank to the end of the pipe; while not absolutely necessary it makes opening and closing the sides quick and easy. On a sunny day the temperature inside can climb into the high 90s, even if the weather outside is cold, so it’s important to be able to open the sides to vent the heat.
Cold Weather Is Here
Now that cold weather is here we have the sides down most days. It’s cold outside (at least it seems cold to us Texans), but it’s nice and toasty inside. Without heat, on a cloudy day the temperature inside is usually 5-10° above the outside temp. On a sunny day it could easily be 20-40° warmer.
I’ve built out the inside with tables for seed starts and microgreens. We now have two separate aquaponic systems. In the photo below, you can see the four grow beds—two on the right and two on the left. The grow beds on the left are recently completed, and we’re cycling the system right now – it’s almost fully cycled! The ones on the right have been fully cycled for months, and are verging on becoming a jungle. We regularly have to go in and hack back the nasturtium. The tall plants that you can see growing up the frame are cherry tomatoes. Yes, it is December.
We do have many days and nights below freezing here, so we had a propane tank installed and hooked up Mr. Heater. It’s just a basic 30,000 btu blue flame heater, but its best feature is that it’s ventless, which means low installation cost. Last week when the temperature was below freezing for the entire week and all our outside water froze, the greenhouse was nice and warm and never got below 45° inside. While I like Mr. Heater, next year I’m hoping to look into warming the greenhouse using compost instead of propane.
We’ve set up a washing, cutting, & packing area in the back of the greenhouse. This is a wonderful addition because we can wash our hands right there in the greenhouse before working. It’s a wonderfully convenient place to harvest microgreens, and it’s easy to sanitize so that we can maintain high quality and good safety. Everything that we need to harvest and pack is right there where we need it.
Here are some of the things we have growing inside right now:
Raft Bed Construction
Our next project is raft beds for the aquaponic system, also known as deep water culture (DWC). Water will drain out of the gravel media grow beds, where it is filtered by the media, plant roots, and the nitrification process. Nitrification is the heart and soul of our system and what makes aquaponics work. That’s a topic for another blog post.
The raft beds are basically constructed like a deck, and then I’ll add strong sides and line it with Dura Skrim. We’ll then float “rafts” that will support the plants on the surface of the water. The plant roots hang down into the water and draw nutrients up from the water. We expect to be able to harvest many dozen heads of lettuce each week from this system.
The media beds are plumbed so that they can drain either directly into the fish tank, or out into the raft bed.
Here is a picture of our fish tank, showing the drain from the grow beds.
All a lot of work! And ongoing. We’re never short of things to do. But the end is nigh. After the raft bed is complete we plan to get good at growing greens, work on our consistency and quality, and reap the rewards of our labor for a while.
Then, on to the next greenhouse!
Thanks for reading. I will leave you with this, our aquaponic grow bed from an earthworm’s point of view:
I hesitate to say it’s finished, but the greenhouse is “mostly” finished, and we’re using it! Couldn’t have done it all without Dad’s help (and his impressive tool collection).
The end walls and screens were really hard to put up. We’ve had wind in the 20-mph range consistently all month, which made it impossible to hang fabric on the frame. Finally we had a calm day, and we were able to attach the fabric to the end wall. The end wall fabric is a single sheet of white 40% shadecloth that we doubled over to make it two layers. My dad helped me build the doors and stretch the screens. The screens on the side walls are a single roll of 84″ wide aluminum screen. The screens and the end wall fabric are fastned to the walls first with staples to hold them in place, and then also with strips of lath to provide extra holding friction.
For washing and packaging fresh produce inside the greenhouse we bought a used stainless steel sink from AAA Food Equipment in Austin. Holy cow, that place has just about everything, in any condition from brand new to completely beat up. This sink will be our washing station for fresh greens. We still need to buy a metal table for packaging, but we’ll pick that up later when it becomes an issue.
Here’s a picture of the inside. We also bought those shelves at AAA. They’ll be used for microgreens. We have a wooden worktable, which you can see just to the left. The small house inside is our dry storage. It’s our old plastic mini-greenhouse. The big greenhouse is no shelter from the rain – the shadecloth just lets rain right through! The sides of the mini greenhouse can be zipped up to keep the insides dry when it rains. This is where we’ll store our supplies, seeds, and anything that needs to be kept dry.
We still have to run water and electricity (for the aquaponics) out there. But it’s serviceable and we started our first batch of microgreens yesterday!
The greenhouse shade covering is on! Special thanks to our new neighbors Devin & Katie Rose and our new friend and fellow farmer Kate from Tiger Creek Farm here in Elgin.
For our covering material we chose 60% black shade cloth, which we ordered from Greenhouse Megastore. To get it over we simply tied a rope to two ends of the fabric, tossed the rope over, and pulled. It was a lot easier than everyone thought it would be!
We used tube lock base and clip around the base to secure the cloth to the sides. We secured the ends to the end walls using spring lock base and springs. If we do it again I’ll use the spring lock everywhere because it’s more economical and much easier to work with.
Still to do: we still need to mount the screen on the side walls, and add the fabric and plastic on the end walls. But we’ll leave that for another day.
At Growing Power we learned how to build a hoop house. In fact we actually helped to actually build it. Armed with that experience we decided it was time to build our own hoop house. Our hoop house is similar to the one we built at GrowingPower, but quite a bit taller. The dimensions are 20′ wide by 50′ long.
We decided to use a materials list pretty similar to the one used at GrowingPower. The side walls are constructed of 1 5/8″ chain link line posts, and the hoops are 1 3/8″ chain link tubes. The sides will be screen, and the covering will be shade cloth in the summer and plastic in the winter.
The advantage of using chain link materials is that they are inexpensive, easy to acquire, and easy to work with. On the other hand, I wish the posts and hoops were a little more rigid. I hope to compensate with extra purlins (long braces run the length of the hoop house, tying the hoops together lengthwise), diagonal braces, and strong end walls. Side wall posts are placed at 5′ intervals. Because of our location we get some pretty strong sustained winds for much of the year. If we were building a larger greenhouse I would not consider using these materials – I would opt for much more rigid materials. However I think they’ll work – we shall see.
The Bending Jig
We built our own bending jig to bend the hoops. This jig was exactly like the one that was demonstrated at GrowingPower. It’s built by drawing an arc on a sheet of plywood, and then attaching blocks of wood on the line of the arc, and finally attaching two sheets of lath to the edge of the blocks to create a smooth curved surface on which to bend the hoops. The radius of the jig is slightly smaller than the actual radius of the hoops. This particular jig bends the pipes just right for a 20′ wide structure.Continue reading The Greenhouse