Tubes are connected by pieces of the same clear, vinyl tubing used in G
“Coil” units can sit inside black, plastic trays 35 cm long x 19.5 cm wide x 2.4 cm deep. A piece of clear, rigid plastic is available to cover a tray with a coiled unit inside.
“Tube” units can sit on top of but not inside the black trays. A piece a rigid, clear plastic could be laid on top of the tube unit.
Black paper, white paper, aluminum foil, and thin, white foam sheets are available to lay over or under the units.
Things to think about when choosing the heater unit:
the color of the tubing the tubing material the thickness of the tubing wall the volume of water contained in the tubing