As winters coming up, I've been experimenting with with hydroponics for some indoor growing during the colder weather. I've already built a 160w CFL grow light, may as well put it to use.
This design uses a combination of a top drip and a deep water culture (DWC) hydroponic system. I chose this as it provides redundancy should either the water pump (top drip) or air pump (DWC) fail and increases simplicity as you don't have to monitor water levels as closely.
A top drip hydroponics system delivers its nutrient solution through a drip at the base of each plant using a water pump where a DWC system keeps the roots submerged within the nutrient reservoir and keeps the mixture heavily oxygenated using an air pump.
This design uses a manifold made from poly pipe to distribute the nutrients to each plant and a small bubble bar with an air pump to oxygenate the nutrient reservoir.
I've marked 12 slots across the lid and drilled them out with a holesaw. There's also an entry and exit point for the top drip pipework on either side. A few drainage points were later added at the low spots of the lid as a fail-safe.
The body of the unit is just a plastic tub. I've made both 30ltr and 50ltr versions. I created a notch with a drill bit and a saw to allow the cables from the water and air pump to pass through.
The manifold is made from poly pipe, 4 elbows and 2 tee pieces. Each emitter is added by poking a hole in the pipe and inserting a 4mm joiner with tubing. It's easier if you leave more tube than required and clip it back to size.
I've chosen to draw the nutrients through an irrigation filter. This is optional however I like to transplant seedlings from my local hardware stores and this prevents soil and other debris from clogging the emitters.
I couldn't attach the pump directly to the bottom of the filter as the tub isn't tall enough so an elbow was added. The nutrients pass through the pump, the filter and then into the manifold to be distributed to the plants. A valve is added to exit point to control the flow from the emitters.
This unit uses an old fountain water pump I had laying around. It doesn't really require a strong pump as you can adjust the pressure with the exit valve. To allow for easy water changes, I've added a tap to the front of the unit. The tap is sealed in place with drinking water safe silicone.
My local hydroponics store didn't have the net cups in the size I needed, so I had to use standard seedling cups and cut slits with a dremel.
An aquarium air pump with a small bubble bar hot glued to the base provides oxygen to the nutrients.
You need a separate nutrient solution during the vegetative (growing) phase and the flowering (blooming) phase of a plants growth. As I plan on growing greens and herbs, I only need the vegetative nutrient solution.
Nutrients usually come in two part solutions but I'm keeping life simple and using a single part nutrient. Once the silicon has cured, the system is filled with water. Time to measure the pH.
Straight from the tap, it measures in the high 7's. A friendly pH for most plants is around 6.0 which can be accomplished by adding pH down at the manufacturers spec. This will slowly creep back up during the systems operation.
I've added hydroton (clay pellets) to my net cups and set the light cycle to 18 hours light 6 hours darkness. Any inert rock will also work fine as a grow medium. When the lights are active, water is pumped for 15 minutes every 2 hours. I'm using standard mechanical timers so I can only set the timing in 15 minute intervals.
Each fortnight, I drain the reservoir and add the nutrient solution to the manufacturers spec.
Ideally, you would want a ppm meter to measure the amount of nutrient in the reservoir however with regular water changes this isn't essential. It's worth noting that you could still build a functional system with either the top feed or DWC component alone.
With space being at a premium, I decided I needed more basil than spinach so I let it run free and it went pretty crazy. I plan on setting up a time lapse camera with various plant varieties, stay tuned!