Take your empty propane tank to a facility that sells liquid anhydrous ammonia. Because the boiling point of anhydrous ammonia is minus 28 degrees Fahrenheit, you need a pressurized container to acquire it.

Connect one side of one of the T-shaped elbows to one end of the first piece of stainless steel pipe. Connect the shut-off valve to the other side of the T. Attach another piece of pipe to the remaining outlet from the T-elbow. Turn the shut-off valve to the full "Off" position (clockwise until it stops).

Add one side of a T-shaped elbow to the end of the second piece of pipe. Connect a shorter piece to the middle of this elbow, and attach the pressure relief valve here. Connect the other end of the discharge valve to another piece of pipe. Attach an elbow to that piece, and then another pipe running back toward the ground.

Attach a piece of pipe to the other side of the T-shaped elbow from Step 3. Run the other end of this pipe into the middle valve of another T-shaped elbow. Attach the charging valve to one of the sides and the other to the last piece of pipe.

Connect this last piece of pipe to the top of the fire extinguishing tank. Set the propane tank in the aquarium on a table outside, next to a plastic bucket, and cover the top with plastic wrap, leaving room for the pipe. Connect the first piece of pipe to the exit valve at the top of the propane tank and bring the wrap snugly around it. The fire extinguisher tank should rest in the bucket.

Add water to the bucket until the fire extinguisher container is submerged. When the aquarium has heated the propane tank to 255 degrees Fahrenheit, the liquid anhydrous ammonia will leave the propane tank, traveling through it to the fire extinguisher vessel, where its boiling will consume the heat, bringing the temperature close to 0 degrees Fahrenheit. The water around the fire extinguisher tank will turn to ice.