Public Lab Research note

Early (2014) plant filter prototype

by liz , nshapiro | May 16, 2017 17:30 16 May 17:30 | #14201 | #14201

First prototype

This was developed in a workshop at App State University in the fall of 2014. The setup adapts an existing pot with holes in it (this patching technique is not advised as it may introduce VOCs into the system) and also uses a flowmeter to assess the flow rate of the system, which is not necessary for daily use.


Start By sealing all but one hole in the bottom of the flower pot. (This open hole will be used to insert the aquarium tube) Make sure that the holes are tightly sealed to avoid water leakage.



Insert one section of the tubing in the hole (roughly 5" into the pot. avoid crimping the tube), and seal the hole around the tube with the epoxy.



Fill the pot with 3 inches of growth medium ensuring that the tube is above the rocks.


Attach the airstone intake to the tube inside the pot and cover with more rocks. Mark on the outside of the pot where the bottom of the intake is. This will act as a fill line when watering. If water is above this line, it will get sucked into the intake.


Cover the intake with another 1 in of rocks or growth medium of choice.



Next, place the plant on top of the rocks and secure more rocks or growth medium around the roots of the plant. Secure the plant around the roots. (Leave an inch in between the root systems and the air intake system to avoid suffocating the filter without losing air flow within the plant system.)



Next, attach a valve connector to the outside part of the tube. This is the end coming out of the pot. You can run any necessary length of tubing from this connector to the intake of the flow meter (the intake and outtake of the flow meter should be equipped with the conversion valves mentioned in materials.)



Next attach the tubing from the outtake to the vacuum pump. See below on how to convert the aquarium pump into a vacuum pump.


Reversing Pump and setting up flow meter with valves.

The first step is to reverse the diaphragm in the pump to convert it to a vacuum. Open up the four Philips head screws on the belly of the pump. Lift up, rotate 180 degrees, and then replace the diaphragm as indicated in the below GIF.

Attach a small segment of airline tubing from the pump to the top of the flow meter (which you have equipped with the conversion valves at both openings) and then attach another small section of tubing to the bottom of the flow meter. You will have three points where you can adjust the flow rate (the meter, and both conversion valves). Open all valves to their most open--while still sealed--position. Once you've started the pump, use the large valve on the flow meter to regulate the flow rate down to .3 liters per minute (or 300 ml per minute).


Notes (to be cleaned up later): Gently separate (we're using mother-in-law's tongue) plants, remove dirt from plants We then filled the pot with recycled glass 3" up from the top, placed our filter in it, then filled another inch of rocks, placed the plant, and then filled the pot with rocks.

test air flow w/ flow meter each configuration before placing in the pot- 0.65 liters per minute (discard-a-stone coarse bubble), 0.7 liters per minute (aqua mist 1 cm), 0.65 liters per minute (aqua mist 5 cm x 14 cm)

Tube length has a negligible effect on air flow- we tested both short (4") and long (6') and saw little difference between the two. Is there a limit for how much air flow is too much for the plant? (temperature difference, etc.)

epoxy to fill in the holes of the plastic pot that we're using (BE SURE TO THOROUGHLY SEAL HOLES), seran wrap should work as well; use one of the existing holes to run the tube through the pot. It's useful to find a pot that has sufficient gaps to run the tubing underneath without crimping. Leave enough room with the tube to have at least a few inches running outside of the pot, Make sure to have enough tubing to allow the filter used to sit above the water level.

Leave an inch in between the root systems and the air intake system to avoid suffocating the filter without losing air flow within the plant system. With this setup, we're getting 0.95 liters per minute of airflow.

to reverse the motor remove diaphragm from the pump and reverse it- vacuum bingo! (GIF LOCATION)

More information on plant types usable for the kit:


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