Flow meters?

[nordy]

I have a new canister filter (Magnum 350) and even though I can see the filter, and how dirty it becomes, through the clear tank cover I would like to be able to measure output and set a level at which I just go ahead and change out the filter media.
Anybody have any experience or advice on this question?
Thanks!

 

[scsinet]

Tom Aquatics makes an inline flow meter that attaches directly to vinyl hose. That should work perfectly for this application. The "marine version of home depot" and the site run by two doctors both stock them.