Good work, well this is what hobby is all about
. Only thing I wonder is will the water flow be adversely affected by the big airstone obstruction in the piping? Is it possible to bubble through the "normal" airstone in the 1st place? (I had to use the 'special' fine ones that will actually diffuses the CO2 - alot more expensive, 2-3 bubbles per sec may not work with normal airstone I think). Also, beware of leakage over time.
Good work tho