[biofilms & biodiversity]

Rack Design & Construction

Biofilm On A String | Biofilm Pipeline | CD Pipeline

Biofilm On A String

[rack schematic 1]

Our first design of the collection rack is simple and inexpensive to build. The diagrams below show how to assemble the rack.

After a hole was drilled in the center of the 10 cm plexiglass discs, a narrow slit was cut from the center out to the edge. The slit allows the user to slide the disc off the fishing line and to remove an individual disc from the rack. <

[rack schematic 2]

The diagram to the left illustrates how the male/female threaded PVC coupling fits through the hole in the center of the disc and is tightened until the disc is held in place between them.

The plastic washer has a slightly greater diameter than the male/female PVC coupling and supports it from the bottom.

The split shot is pressed on to the line just below the plastic washer and voila, the disc is held in place at a predetermined location. There are many interesting experiments that can evolve by varying the depth of the discs and the distance the discs are placed from one another along the line.

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Biofilm On A String:
Step By Step Instructions


[rack material]
Gather all the necessary materials: plexiglass discs with holes and slots cut into them, male/female PVC coupling that will fit the hole, heavy fishing line or string trimmer line, washers and a metal clip to hold the unit in place on the line.


[rack coupling 1]

[rack coupling 2]
Place the male coupling through the hole of the disc and thread the female coupling onto the other side of the disc until it is held firmly by the PVC coupling.

Tip: The size of the hole in the disc is not crucial just be sure that it matches the size of a coupling that is readily available. We like to use male/female PVC couplings that have a diameter of 1/2".


[threading the string]
Thread the string through the coupling.


[washer below coupling]
Place the washer below the threaded coupling unit and put a clip on the line to hold the unit in place.

Tip: The clip that holds the unit in place on the line can be split shot, a brass clip for fishing line, a cotter pin or other sturdy material. The clip will determine the location of the unit on the line.

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