Is gph cumulative?

[abpechman]

We were wondering if two canister filters that push 400gph in the same tank means they really are cumulatively pushing 800gph?  Or is it just a matter that it is two 400gph filters working more efficiently?  

In a 100g tank that will have a variety of loaches and botia how many times per hour should the tank "turn over?"

[JLawson]

Re: Is gph cumulative?

It seems to me that if both filters are removing/returning 400 gph then yes... you have a total turn-over of 800 gph.  Does that mean you are achieving TWICE the actual filtration of just a single filter - I don't think so.

The important thing about filtration, of course, is moving "dirty" water through the media to be returned as "fresh."  When multiple filters are used, each filter is processing a relatively lower concentration of pollutants than if it were doing the job alone.  The results are additive in that two filters will remove more pollution than one - but I don't think they remove twice as much as one filter.  There are so many variables that will affect this such as placement of intakes and returns relative to one another and those of the other filters, are there circulation "dead spots" in the tank, do feeding practices concentrate uneaten food closer to one filter than another, are all filters using exactly the same media and in the same proportion, etc.

As for optimal turn-over rates, I've seen references that suggest 5-6 per hour is adequate under most circumstances.  I've heard other people say they prefer something closer to 10 per hour.  The guideline that you choose may not be as important as what your water tests tell you.  Given your current filtration arrangement and your tank's current bio-load, if your ammonia and nitrite levels are where they should be (0 ppm) then you have adequate filtration - if not then something needs to change.

[eklikewhoa]

Re: Is gph cumulative?

Two 400gph filters will have a total of 800gph and two filters will be twice as effiecient as one filter.

community tanks I go for 4-6x
planted tanks 2-4x
cichlids 10-20x

[PhishPhreek]

Re: Is gph cumulative?

If you run two pumps in parallel (one left side & one right) the total flow will be the sum of the two flow rates.

If you run two pumps in series the flow rate will be the smaller of the two
but the head will be the sum of the two.

[Tiapan]

Re: Is gph cumulative?

5 to 6 times an hour really is more then enough typicallly, now a salt tank i prefer more so that the water goes through the bio load more often preventing chemical spikes. and in an overcrowded tank extra filtration help to a certain extent. at least till you use up the surface O2 exchange. then you can add an air pump and stone

[geoff_tropheus]

Re: Is gph cumulative?

Two filters at 400 gph will move 800 gph as long as their discharge tubing/piping is not connected.

Also, one may clogg faster due to its location..i.e the end that you feed from or waste collection in the tank.

The pumps on the canister filter will only move what the media will allow it to move that is if the canister has no bypass.

[abpechman]

Re: Is gph cumulative?

Thank You for all the information so far!  It really has helped us clarify this question we had.