Hi All,
I got some new tubing in today from Aqua Essentials and am happy to report it works a treat. Just so people know which one I used, it was
https://www.aquaessentials.co.uk/neutro-clear-co2-tubing-per-metre-p-2095.html
Bubbles are really fine, well when compared with the glass Blau one I used previously.
Running my system on 40 psi and its seems to be totally fine.
For test purposes I have tried to lower the psi, and by the time it got to around 25, it had really slowed down to almost nothing coming out of the diffuser, so I don't really believe that it will run on 4psi.
Interestingly, the tubing from Aqua Essentials is softer and more pliable than that that of Co2Art, so I am guessing this helps it create a better seal around the Neo diffuser. Though I also agree that the Neo one could probably do with a small nipple to help create a nice seal, though with this slightly softer tubing it does still work. The tubing is not as soft as standard airline tubing, but again still softer than the Co2Art one.
Overall good experience with Co2Art for me, especially when my first diffuser was playing up, but it just seems their tubing is not compatible with any diffuser that does not have a nipple to create a seal.
Hope this is helpful to someone!