Please note, the mazzei venturi has trade offs, every method nutrients, cO2, light, tanks etc does..........
Looking at these trade offs and seeing which is best for you is the key focus here.
Mazzei:
These need higher flow rates/pressures.
So unless you have a external pump, 600-1200gph ranges, do not bother.
You can do sump applications using larger powerheads etc.
But if you have a sump, might as well just use the return pump's impeller then.
The reducing Tee allows you not to lose any flow and add it in line post canister filter, or in the return tube etc.
This requires a check valve, 2 ideally(redundant back up).
You may also add a Tee to inlet, one from the CO2 tank and then one from a small air pump, you need a check vlave for each line so the CO2 does not go out the air pump obviously and the backpressure in the filter line does not back up into the CO2 or air pump.
This way, you can add aeration at night using a timer and CO2 during the day.
Very simple modification.
This will degas and keep O2 higher when you need it, and CO2 high when you need it and low when you do not.
Another solution that is similar to the Reducing Tee, is the CalAqua lab's diffuser:
http://www.aquaessentials.co.uk/index.p ... ts_id=2143
Cost a bit more and easy to break(don't ask).
Another similar version is a DIY PCV threaded screw adapter, that goes from the return line size to a larger diameter and you drill a hole to add the CO2 line and glue to prevent leaks. Then you place an air stone inside this, pretty much like a DIY ugly version of the CAL CO2 in line stone above.
Or you can run a DIY reactor tube.
I think the Reducing Tee is fine and works well on good sized tanks.
I use more flow in the tank itself to blast the froth around, but you get far better mist using a mazzei than with these other methods.
But the smaller tanks, it's less of an issue.
So the trade offs work well and give more options and in line vs sump applications.
Regards,
Tom Barr