Introduction: The Basil Box - Compact and Affordable Hydroponic Deep Water Cultivation

      Last year I followed this Instructable  to build a hydroponic garden and it turned out really nice. I used it to grow lettuce, basil, and tomatoes. After a couple months, the lettuce started bolting and flowering and the tomatoes outgrew the setup. In the end, I used the setup to grow three basil plants for about six months. It took up a whole lot of space, required a large amount of water and nutrients in the reservoir, and got dirty very quick. I started to pack it all up for a move but it was so slimy, moldy, and gross I decided to salvage the valuable parts and trash the rest. I missed the bunches of fresh basil (hence the code name "The Basil Box") so I decided to draw up a design for a setup that would take up less space and could be cleaned/maintained easier. The objectives I took into consideration for this design were:
  • Reasonably Priced
  • Easy to Maintain (adding nutrients and adjusting lights)
  • Easy to Clean
  • Easy to Break Down and Pack Away When Not in Use
  • Small Form Factor (Final dimensions were about 1.25 ft x 1.25 ft x 2.5 ft)

Step 1: Plans and Bill of Material

      Keeping this project cheap was the main objective I wanted to stick to. Luckily I had most of the hydroponic supplies on hand, so the total project cost for me was under $50. Those just starting off with hydroponics will need to buy a few key materials such as expanded clay, pH control chemicals, an air pump with air stones, and nutrients in order to get their system up and running. I've included the preliminary sketches I drew up (Some dimensions on the drawings have changed) and the BOM.

Step 2: Water Reservoir

      I chose a DWC or deep water cultivation system design because of their simple setup and few parts. A basic DWC system uses a water container, a planting pot that is submerged in the water/nutrients, and an air pump placed in the water to supply the roots with oxygen. The first step to build the water reservoir is trace the 5" pot outline on the center of the lid of a 2 gallon bucket. Then shrink the dimensions by about 1/4" so the pot would sit nicely in hole that will be cut. I used a Dremel tool to cut the hole and then some rubbing alcohol and a paper towel to remove any leftover marker.  Then drill a 1/4" hole in the lid for the air hose. Next I drilled twelve 1/2" holes on each side using a grid pattern drawn by scraping a knife along the plastic. You may be able to by-pass all this if you can find a 2 gallon net-pot lid, but I had the square pot laying around.

     To supply the roots with oxygen, I made a quad air-stone setup with 3 drip irrigation tees, some tubing, and a four pack of air-stones. You could alternatively buy a larger air stone and cut out the cost of buying the drip irrigation kit from Harbor Freight but these small air-stones were the only ones available at the time and I had leftover fittings from the cheap drip irrigation kit.

Step 3: PVC Pipe Lengths and Bottom Frame

     I attached a chart of all the lengths of 3/4" PVC pipe needed for this project. I used a cheap $7 miter box from Home Depot to cut nice straight lengths and I recommend it. It just makes things easier. I de-burred each piece with a x-acto knife to get rid of any rough edges. To construct the bottom frame, you will use the four 12" sections, four 90 degree outlets, and four 1/2" Thread to 3/4 PVC adapters to make a square base. Then slide in the four 16" legs.

Step 4: Top Frame and Lighting

     To start the top frame and light, the first thing you'll want to do is glue your two weatherproof sockets into the 1-1/4" tees sot hey have time to dry. I used gorilla glue since it cures pretty quickly. You can put the four 1-1/4" X 3/4" bushings into the tees at this time as well. Next, take the four 5-1/2" PVC lengths and connect them into the two 3/4" tees. These tees will stand straight up and provide a mounting location for the cardboard reflector. I used two plugs to add a bit more length to stabilize the reflector but you can just use short lengths of 3/4" PVC if needed. You can attach all the 1/2" threaded to 3/4" adapters to the 90 degree outlets at this time.
     The lighting and wiring is probably the most challenging portion of this project. The fittings and wires had some tight fits and you have to ensure that the wire nuts are securely fastened.  Start by taking one of the reflector mount sides and attaching two 90 degree outlet combos to each side. Attach one 2" length and one 6" length to the other open ends of the outlets. Attach one 1-1/4" light socket tee combo to each side with both sets of wires pointing up. I offset the length of hot wire and ground wire on each connection to allow for proper separation of wire nuts. Wire up the first light socket with two wire nuts and thread on the one remaining PVC length for that side and a 90 degree outlet. Thread the wire through the second reflector support side. Drill a 1/4" hole into the last 90 degree outlet, push the lamp cord that will plug into the wall through, and thread on the last section of PVC pipe. You should now have a set of wires coming from the wall plug, a set of wires coming from the first light socket, and a set of wires coming from the second light socket. Wire all three hot wires together and all three ground wires together with two wire nuts. Shove excess wire and wire nuts into the PVC pipe and press together. I did not use glue on any of the frame in case I wanted to salvage any parts or repair any wiring problems. Also note that the 1-1/4th tees can be twisted to adjust the light bulbs. Hopefully the pictures do a better job of explaining the steps if they sound confusing but if not, feel free to ask. I've included a quick wiring sketch to show how things go together as well. At this point you can test your wiring and make sure both lights work.

Step 5: Reflector and Final Touches

     Once the top lighting frame is complete the cardboard reflector can be made. Make sure the top frame fits onto the base/legs before tracing and cutting your reflector to avoid incorrect dimensions. Flip the top frame over and set it on a large piece of cardboard. Trace an outline of the frame, including the mounting tee holes, and cut it with a box cutter. Cover it with aluminum foil/tape and make sure it fits nicely on the top frame mounting tees. If you bought the four optional couplings (which I recommend in order to adjust the height of the lights during your plant's growth) you should also cut four ~7" pieces of PVC to use as extensions. I attached the air pump to the frame to keep the unit compact, but it isn't necessary. I used two zip ties and a small piece of cardboard to attach my pump.

Step 6: Setup

     The first thing you want to do with your brand new hydroponic system is SANITIZE EVERYTHING with some diluted bleach solution.  I've had previous systems get completely covered with mold because I did not sanitize the growth medium and water reservoir first. I bought a basil plant to use with my setup, but you can definitely start something by seed or cutting. I sprayed off as much dirt as I could with the hose and planted the basil. Before adding your plant to the water reservoir, you will need to prepare the water. First, you need to measure the pH. As you can see, the water out of my tap is around 8.0. I usually shoot for the 5.0-6.0 pH range. I adjusted my 2 gallons of water with about 1 ml of GH pH down solution. For nutrients, I had leftover GH Flora Series nutrients. On the back of the bottles, there are charts to follow to mix your nutrients. I ended up using 10 ml of each nutrients for the "general growth" ratio but I have heard 1/2 the recommended amounts will provide the same effect (they just want you to buy more nutrients). IMPORTANT: Measure the pH once more to make sure your nutrients did not throw off the pH too much! I've read that basil needs around 10 hours of light a day so I set my lamp timer to that duration. Attach  the pump to the air stone with about 1-1/2' of tubing from the drip irrigation kit and that's pretty much it! I have pictures of both Basil Box setups - one with 16" legs and one 16" legs + 7" extensions. The final two pictures show the progression of growth after just one week. 

Step 7: Conclusion

     After two weeks, the basil seems to be thriving. I've attached an animation showing the time lapse of the growth. The gif did not play. Check it out on my site if you're interested HERE. The leaves are much larger and darker than the same type of basil growing in dirt. When the basil outgrows your Basil Box, prune it by cutting the main stalk as close as you can to the 45 degree angle sprouts like the picture. If you don't want to buy a basil plant and have one available, cut off the top of it, just like you were pruning it, and stick it in a glass of water. After around week, you should have a bunch of new roots.
     This was a wonderful project and it was fairly easy. It only took around 4 hours on a Saturday to construct and a I'm sure it'll satisfy all of my basil needs! Feel free to visit my website Cooking Circuits for more pictures and details on this build or a new project idea!

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