This is a summary of our build and experience so far.
Our window frame measures 75” x 31” so we thought two columns with five rows (ten containers total) would work well. We decided to use the recommended 1.5 liter water bottles for the containers, but instead of cutting one outlet per bottle, we decided to cut two on opposite sides and have two plants in each container. Each column is attached to a single wire cable that hangs from its own plant hook, loops through the bottom container, and back up. Wood dowels are inserted through each bottle (except bottom bottle) and alligator clamps hot glued to the wood dowels attach to the wire cable. Duct tape covers the bottom of the bottles to prevent the roots from drying out and minimize algae and mold growth. Rather than filling the net pots with clay pellets and then inserting the pot into the bottle, we eliminated the net cups, filled each bottle with the clay pellets, and the plants go directly into the bottles.
After reading about other farms, we first decided to go with the upper and lower reservoir system utilizing a water pump. After getting our supplies, the next step was to set up the watering system. We soon realized that to pump water over six feet vertically was going to require a heavy duty and more expensive water pump. We returned to Home Depot to purchase a fountain pump capable of 400GPH at 1’ lift, with a maximum lift of 7.3’ at $40.00. We then realized that due to the size of the pump, it would have to sit outside of our bottom reservoir, meaning we were going to have to consider the sealing aspect of our system to prevent water leakage. Our other thoughts about the water pump were the noise of the pump, the power usage, and fear of running the pump dry, which would mean we would have to go to a clear bottom reservoir to know when the water level was getting low to shut the pump off. With all of this adding up, we decided to ditch the water pump system, and move to the air pump system.
We purchased a Top Fin Air Pump 4000 with two adjustable airflow outlets for use with up to 80 gallon aquariums. Without looking at any diagrams or suggestions for the air lift system, we started experimenting with different ways to get the system to work. After days and days of different setups, numerous trips to Home Depot and PetSmart purchasing and returning products, and frustration beyond belief, we finally broke down and read other posts on the setup. After reviewing the recommended airlift setup and combining what we had already learned, and a bit by accident, we came up with a new airlift setup that works incredibly well and reduces gurgling. See our diagram below. As others have mentioned, the depth of the water is the greatest factor in achieving lift. Our bottom reservoir is a glass cylinder measuring only 4” diameter, however, the container stands 13.5” tall. When this is filled to 9.5” the max lift we recorded was 5’ 4”. When filled full at 13.25” we achieve an 8’ 3” lift, though 7’ 3” appears to be the optimal level for this water depth. Also as others have stated, keeping the air lift tube as straight as possible, especially into the reservoir helps achieve better lift.
What is excellent about the air lift system (once working) over the water pump system is the reduced cost of the setup, simplistic design and setup eliminating the top reservoir and having to seal and water proof the system, virtually noise free (no loud water pump), not having to worry about running the pump dry and damaging the unit, and the reduced operational cost (water pump consumes 80.5Watts versus air pump at 3.5Watts). Not only this, but the water pump system also suggests using an air pump in addition to the water pump to aerate the water so it does not become stagnant and reduces mold/algae from standing water in the bottom reservoir.
Our Plants
We decided to grow strawberries in 8 of the 10 containers, and peas in the other 2. Using clay pellets with no soil, we purchased organic plant nutrient (liquid form) that says it is designed for soil and soilless gardens. We mixed the recommended amount of nutrients to water and filled our reservoir. During the day we would leave the air pump running and the water/nutrient solution would trickle down through our plants, and turn the pump off at night. Everyday we added about ¾ cups water due to plant use and evaporation. After about 4 days our mixture had become clearer indicating a higher water base than nutrient. Though our peas are fine, the strawberries after about the fourth day began to show a little black on the ends of the leaves, and after six days, some of the leaves were yellowing. What is interesting is that the strawberries closer to the top of the window farm show little to no signs of the discoloration. This indicates that the problem might be from a lack of nutrients to the lower strawberries.
We found out several things and are currently correcting those to see if it makes any changes. First, although the nutrient mixture said it was for soilless systems, this apparently refers to mulch, and not hydroponics. It also contained only nitrogen, phosphorus, and potash, but no calcium or other minerals which we read can contribute to our problem. We have now switched over to a dedicated hydroponic nutrient formula containing calcium. We have also been told that consistent watering and then drying out can be harmful to the plants. We purchased a timer that turns the pump on 15 minutes of every hour during light, and 15 minutes every two hours when dark. We also purchased a pH tester, although we might also purchase a tester for nitrogen, phosphorus, and potash.
Below is a table of our materials and costs. This is an approximate estimate and you will see it is a bit more than the $30 mentioned on the window farm web site:)
This list only shows what we are currently using. It does not take into account extra tubing, needles, miscellaneous aquarium supplies, and the first nutrient solution, as these were items we tried but did not end up using.
Structural and System Costs
| Item |
Description |
Cost |
| Water bottles |
Although you can find these recycled, we wanted to get going on our system and just purchased the bottles, plus we wanted them all uniform |
$1.70×10=$17 |
| Ceiling hooks |
2 pack |
$3 |
| Wire cable |
Used for hanging the containers 78”x4=312”/12”=26’ |
26’x$0.25≈$6 |
| Duct tape |
For masking off the 1.5 liter bottles |
$3 |
| Wood dowels |
Supports each 1.5 liter container |
$2 |
| Alligator clips |
6 pack. Attaches dowels to wire cable |
$3×4=$12 |
| Clear tube |
For airlift tubing3/8”x1/4”x10’ qty2 |
$3×2=$6.00 |
| Clear tube |
Standard aquarium tubing for air pump 10’ smallest they had. Needs to have 3/8” OD to fit tightly into airlift tube |
$3 |
| Needles |
Ball pump inflation needles 2 pack |
$2 |
| Air pump |
Top Fin 4000, 2 adjustable outlets, up to 80gallon aquariums |
$20 |
| Glass container |
For bottom reservoir. 4” diameter x 13.5” high |
$10 |
| Timer |
Hydro Farm single outlet 24 hour mechanical timer |
$14 |
| Hot glue |
Attaches wood dowels to alligator clips, and helps seal some of the bottles from leaks |
$2 |
| Total |
|
$100 |
Plant and Formula Costs
| Item |
Description |
Cost |
| Clay pellets |
Used instead of soil for hydroponic system |
$12 |
| Plants |
16 strawberry plants, 4 pea plants |
$20 |
| Nutrient formula |
Canna Aqua Vega A: 5-0-3, and Canna Aqua Vega B: 0-3-4 |
$26 |
| pH test kit |
Simple glass vile with pH solution |
$7 |
| Total |
|
$65 |
Total build cost = $165
Additional tools needed:
- Hot glue gun
- Drill with drill bits
- Exacto knife
- Scissors
Thanks for the fun adventure windowfarm.org
We will keep posting updates as our system grows!
Britta and I finished the first window farm prototype in her kitchen window in April. The system includes a pump in a bottom reservoir which is on a timer, to pump about 3 gallons of water/nutrient solution up to the top reservoir. The liquid then drips through the columns of water bottles that hold the plants.
- 500+ gallon per hour pump of high quality which makes it quieter. You can go with a cheaper one if like this it will only turn on 3 times a day.
Reservoir 2 above the window
Water Bottles
