Maybe where the main filter flow is directed?
I have 2x Fluval G6 in my 200L. These have an actual flow of 1000 LPH (2460 LPH pump performance) each so I'm on just over 10x actual turnover. If fish get right in front of the filter output then they have a job swimming too.
A spraybar softens this 'intense' jet of water and improves flow in a lot of cases.
Wow thats some good filters, your all making me feel i need some more filtration, maybe i will use another filter and with that put the reactor on so if flow is restricted by reactor which it will, i will still have good fliw on other filter
Thanks all for the advice