Thanks guys. It turns out the compression threads are pretty important. It started to leak and so I just used one of the adaptors to join the tubing back together with no leaks.
Here's the thing. I am thee laziest person ever when it comes to having to go out of my way so right now the thought of sorting out a reorder and ordering the 'correct' one is not going down to well right Now. I'm kinda split in how I want to play this.
Whilst I had the canister out I made a few changes that has increased my co2 saturation. Obviously not as efficient as an inline but I managed to get a green drop checker and about a 0.9 ph drop albeit two hours before lights out. I'm gonna play it this way for a week or two to see if I can solve this issue. I started to get hair algae which is a sure sign of low co2. Also improved flow. I just have to ensure the low co2 doesn't upset my fish again.
Sent from my iPhone using Aquarium Advice