You Hear Noises and things !!!
After reading all the posted comments here, There is 1 Major & Important Over sight.
When it comes to Rattling, Nosies, ETC, This is all to do with AIR LOCKS.
What has not been said is how to properly remove them.
This is the easy part. Do not rely soley on the Caniters to do the job. After all, when 2 pieces of plastic are joined together with water in the middle You are by the grace of god will have trapped air..
After setting up & Priming your Units, TURN OFF THE FILTER PUMP, Lower the OUT FLOW hose into a bucket at floor level, Switch the filter pump back on, this method allows the head of the Pump to syphon itself, Here you will be able to see the Bubbles (AIR LOCKS) in the hose.
When all the Air has gone, You will now have a quite System
Of all the Filter systems I have had over the past 30 Years, The above method always works on all Filters. Hope I have helped