Over Filtering - Page 2 - Tropical Fish Keeping - Aquarium fish care and resources
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post #11 of 17 Old 08-31-2011, 05:09 PM
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Originally Posted by stevenjohn21 View Post
I just feel that a higher flow rate going through as much media as you can manage to put in the filter would be better all round .
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Well, it is not. And please don't take that offensively, it is just that this is another of those "myths" that are out there.

With respect, you don't seem to understand fully the tasks that a filter manage. First, there is a big difference between cleaning the water and clearing the water. Mechanical filtration--moving water through any media, esp the wool pads/sponge/floss--is clearing the water by removing suspended particulate matter. I don't have statistics but I think it is highly debatable how effective more of this can possibly be in any tank. And as someone mentioned, the faster the water goes through this media, the less effective the capturing of the particles will be.

Then we come to the "clean" aspect. This can be biological and chemical. Nothing, and I repeat nothing, does this better than live plants. Now, you need it balanced to be 100% effective, and most of us have more fish in a tank than what will allow this, so the filter equipment gives us some leeway. But again, there is only so much the filter can do.

With respect to biological filtration, involving the nitrification bacteria, there is more of this going on in the substrate and on other hard surfaces than in any filter. And the bacteria will only exist at the level necessary to handle the ammonia/nitrite--no more, no less. So again with the fish load balanced for the tank, there cannot possibly be any advantage to more filters, biologically. And the fact that in well planted tanks biological filtration is detrimental to plant growth anyway and we do not want to encourage it, that is another negative.

The denitrifying and anaerobic bacteria can be forced to increase by too much filtration, provided organics are present to sustain them, and this is not beneficial.

So that brings us to the chemical filtration, using carbon or other substances to alter the water chemistry. This has advantages in non-planted tanks, but is highly detrimental with live plants. And again, the plants can do this task better, so why not let them get on with it?

You can read more on some of these points here:

The bottom line in all this is that there is only so much filtration that can benefit any aquarium. And exceeding this can actually be more detrimental.


Byron Hosking, BMus, MA
Vancouver, BC, Canada

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian. [unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

Last edited by Byron; 08-31-2011 at 05:13 PM.
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post #12 of 17 Old 08-31-2011, 06:06 PM
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i have 30 gallon tank with 60 gallon filter

i have a dog named fish

30g long

55g -planted

125g 4ft long octagonal


10g hospital
-empty- :]
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post #13 of 17 Old 08-31-2011, 09:01 PM Thread Starter
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I don't have any plants or substrate ...
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post #14 of 17 Old 09-01-2011, 01:07 AM
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The notion that faster flow, allow's fine particulates to pass right through mechanical filter material has merit but not enough merit in my view to be of any real concern.
Same material that escaped the mechanical media the first time,will be brought back through in minutes assuming the flow is such,that this escaped material doesn't just fall to the bottom and set there until removed via vaccum.
Filter's are designed to move specific number of gallon's per hour for different size aquarium's to efficiently filter same.(flow is dereased by adding media)
If one want's to decrease flow,,then buy smaller filter.
Filtration for ME ,, is all about species of fishes kept,food's offered,(most over feed their fish) and number's of fish.
Been filtering for a few year's now,and most of my tank's with exception of planted tank's are over filtered.
Has worked well for me and perhap's thousand's of other's as well, Opinion's vary.

The most important medication in your fish medicine cabinet is.. Clean water.
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post #15 of 17 Old 09-01-2011, 01:16 AM
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One must also keep in mind that manufacturers rate their filters without any media in them. So a filter rated at 400 GPH empty will run quite a bit less when stuffed with media.

150 Gallon - Mostly American Cichlids
135 Gallon - Angelfish Community
75 Gallon - Odd couple (Polleni/Angelfish)
55 Gallon - African tank
20 Gallon Long - QT
10 Gallon - Empty
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post #16 of 17 Old 09-01-2011, 09:05 AM
The point is that if the filtration is really good, we shouldn't need to filter all the water in the tank 5 (or 10!) times every hour. If we need that much turnover/flow, the actual filtration must be very poor.

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post #17 of 17 Old 09-01-2011, 10:32 AM
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Is easy to deterime.
Look at water, look at number's and size of fishes,food's offered and frequency,substrate,maint routine,nitrate level's between water changes,how quickly filter media clog's or get's dirty.
These will help you determine if filtration is adequate, and all of the above factor's are different in different tank's.
Easy to underfilter an aquarium in my view.
Ideally,,everyone would stock moderately, not over feed,perform regular maint on filter's and perform frequent water changes to remove dissolved organic's,waste,and suspended particulates that make water dirty.

The most important medication in your fish medicine cabinet is.. Clean water.
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