for all those that enjoy or wish to put their DIY skills to the test,there is another very easy way to make a CO2 diffussor. get one fluidised bed filter canister,fill with miniture bio balls,but ensure that the centre tubing remains because if you remove it, you will never get the tube back to fit.Once filled ,close and plumb to you external power filter. The centre intake of bed filter is connected to the output of your filter and the other goes to the aquarium. Now the tricky part comes, insert a small hole into the tube that goes into the bed filter. One can get a hose tail barb from the irrigation shop(the one used to join 2 pipes together,they are cheap 4-5mm).In the hole that you have just made, squeeze the barb into it,if your hole is not too big it takes a bit of elbow grease, but that is what you want, a tight/leak proof fit. To the barb that you inserted into pipe connect a non return valve(pet shop sells them) then to the CO2. Switch your pump on,turn on the CO2 and by watching the exit water into the aquarium,one can make adjustsments(excess bubbles)and the CO2 diffusors perfectly . It removes the bulky powerheads etc in ones aquarium. enjoy making it. if stuck,APSA me.