I want to put CO2 into my new 275 litre tank and am looking at the JBL
proflora 3 set which comes complete with a PH meter.

Only issue is it (and many of the other sets I've seen) says its for tanks
upto 200 litres. Why is it limited like that? Surely I can just inject gas
at a faster rate in a bigger tank - or is there some issue with the size of
the diffuser? If this is the case can I just put a T piece in the CO2 line &
run 2 diffusers to increase the output?

Lastly what is so special about "CO2 Hoses" - will ordinary airline not work
or will it rot or dissolve or something if used for CO2?

rgds

Iain