Erm...ive never used these, but I am think ingthey might be ideal over my current system whihc is a JBL diffuser. my current aqaurium is 400 litrs and i may upgrade to an 800litre. I have seen the Aqua medic 1000: http://www.aquaticbiotope.co.uk/Scripts ... roduct=827 I am not sure though what 12/16 mm connection hose mean. Does that mean it can connect to 12 and 16 mm internal radius hose? I have a fluval fx5 which has 24mm hosing and an Eheim 2080 which has 16/22mm (i get confused what does that mean, its 16mm internal radius?). So this works by attaching the reactor to the inlet pipe of an external filter? Is there another way of doing it so that you dont reduc filet flow. Can you use a powerhead ( dont know how that would work lol) or an external pump? hmmm maybe just another smaller filter....think clive mentioned that. Do you guys have links to any other co2 reactors? Thanks.