The water circulation system is made from PVC pipes and fittings, that are held together with glue, or PVC cement:
On the left above is a can of special PVC cleaner. It smells awful when applied so I had to open a window to keep my braincells from dying. It’s so strong that it actually dissolves a thin layer on the surface of the PVC, which helps the glue get an even better grip.
The glue bottle comes with a useful brush in the lid to make it easy to apply the glue to the PVC pipes. The glue is applied to both items before assembly:
This is the feeding pipe for the plant tank:
I have connected a short pipe to take the inlet stream below the water surface in order to keep the system quiet, but if noise wasn’t a problem it’s probably best to let the water splash out of the fitting to pick up as much oxygen as possible.
In the other end of the plant tank I have mounted a stand pipe to raise the water level in the tank up to a certain height. The reason for the small holes in the top is to make sure that the floating mats won’t block the drain:
The drain goes through a hole in the bottom of the plant tank and takes a turn to the left:
and the return water flows into the far end of the fish tank:
The hard part of making this drain, besides looking out for whatever braincells I had left (PVC cleaner and glue), was to assemble each PVC part in the correct position before the glue locked the parts together completely – which was about 10 seconds 😀
Next up is the mounting of the water pump.