After removing the spout from the caddy, insert the disk into the screw cap. You now have a lid that will pressure seal the caddy.
a. Drill two holes to accommodate the rigid airline tubing.
b. Silicone or glue the two pieces into the lid and allow to fully cure/dry.
Cut a length of vinyl airline hose that when attached to the inside end of the longer, (five inch) rigid tubing, touches the bottom of the caddy when you screw on the cap. You may wish to attach a "clunker" or other weight to the end of this hose to keep it
from floating off the bottom when in use.
Cut another length of hose to run from this same five inch tubing back to your sump or aquarium. This will attach to the outside exposed end of the same, five inch tube.
Cut a third length of hose to run from the other, shorter tube to the Tetra Luft Pump. There is no other connections to be made. The exposed end of the shorter, three inch tube should extend into the container, BUT NOT TOUCH THE WATER'S SURFACE WHEN
THE CADDY IS FILLED.
Plug the electrical cord from the Tetra Luft Pump to the appliance timer. You are done with the actual construction of your top-off system!