"Ruth" wrote in message
m...
I have two Fluval 404 on a 125 gal tank. One of them has a pretty
good rate of flow out of the output tube and has a little bit of
pressure (not like a faucet, but substantial). The other one has a
terrible flow rate and I can hardly even feel it when I put my finger
near the output tube, even though it is obviously working.

I'm relatively new to this and took over an already-set up tank. Is
there something wrong with the one Fluval, or is this unevenness
normal across filters fo the same model?

Thanks,
Ruth

Their flow rates should be comparable so you are looking for something
which is causing a restriction. This could be anywhere, from the intake
screen, debris in the hoses, build-up in the media etc. If you swap the
2 filter canisters, and the problem follows the filters, then it's
inside, otherwise it's in the hoses. Swap the media boxes and if the
problem follows the box, then the media is clogged, otherwise it would be
a restriction in the head (ie: impeller cavity, shut-off valve etc).
This substitution methods narrows it down to one of 3 places to look.
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