That's just plain bonkers ...surely it'd be easier to grow longer arms...
Read this and don't want to contaminate his journal.I see no good reason to ever add CO2 24/7. ADA and myself are in agreement about a number of things, this is one of them. Amano says it is "taboo"(his words, not mine).
Search for "eheim needle wheel pump". Search images to see when the impeller looks like as well.I did google needlepump, but never heard of one or seen one here in the Netherlands.
Also do 8/12, 12/16 as well as 16/22.UP is a brand name for a ceramic diffuser, they offer inline models but they would not be suitable to use as the pipe fittings are only 16mm.