I know that it’s a pointless venture, I was just wondering. Also, I have two canisters sitting under my tank and I’m worried I’m losing a lot of filtration, suggestions on how to increase flow because of height issues? I can’t move my canisters up because of where it is wife doesn’t want to have them visible.[/QUOTE
I cannot see an advantage for doing this. Assuming that each filter has its set of coarse, medium, and fine mechanical filtration layers, then particulates and debris would be trapped in the first filter and never make it to the second. If the second filter had only biological media, then that’s fine, however, more media does not always mean more beneficial bacteria (as they are limited to the amount of nutrients present).
Disadvantages would be the output of the first filter will most likely not match the intake of the second filter. You will end up with either a negative or positive pressure situation. Also, should one of the filter’s motors fail, then (depending on the design of the impeller housing) it could impede the flow overall.
You are better off just running one or both (one would act as a failsafe).
like said here running through 2 canisters and one motor dies out pulling water through the 2 canisters with media would just about stop the flow. and put a big strain on the pump motor
at first I thought I would have this same issue with 1 canister and 2 pumps
if one pump died would the flow stop. no if the outlet pump died it would run as if t had the one pump from the beginning, if the inlet pump died it would still run as well just at a slower pace because of the strain of pulling the water.
after some trial and error until I got things placed right . because of how the pumps are placed inline if one fails the other would still keep the flow going just at a slower rate , if your intake pump failed your outlet would pull it through putting extra strain on that pump and you would hear it but not any more than if it was running 1 pump all along . not fail safe but would function long enough for repair .
if your outlet pump dies out your inlet pump would work just as hard pushing the water through but like I said it would work long enough till a repair . nothing is fail safe its all trial and error
I've been running like this about a year now so far no issues but I am also always here to monitor if something went wrong,
first you need to find 2 identical inline pumps the stock ones are fine as long as you can match them.
on your intake put your pump inline as close to the intake as you can this will make your intake suction stronger pulling more crud from the water and force the water through your hose to the canister.
outlet side put your second pump about 1/2 way down the hose this will work with your intake pump pulling and pushing water through canister this will give you a higher flow rate out of your outlet .
running the 2 pumps doubled my flow rate if the one pump fail's the other will keep working but at a slower rate the water would still flow through the dead pump. so far I have had good luck with it with regular maintenance
keeping your media clean things can and will run smooth , it's just about how much you like to mac-giver things.
Ive been running this way a little over a year now with no major issues
http://www.aquariumadvice.com/forums/f60/cobalt-4-stage-canister-filter-349675.html