Optimal Flow Rate for Biological Filtration

noiesmo

noiesmo

Candiru
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Jan 11, 2008
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noiesmo.dnsalias.com
OK my question is related to how fast water can flow past bacteria or should be flowing past living bacteria on bio-media in a wet and dry trickle filter. For optimal biological action.

I know as a rule, people look at tank volume and then look at turning that volume of water up to six time through the filtration media. So if tank holds 100 gallons it would have a pump running up to 600 gallons an hour.

However is there not an optimal rate, when looking at certain brand filters for example canister filters they do not all have huge flow rates some only 500 gallons per hour.
 
Mattyou

Mattyou

Piranha
MFK Member
Mar 12, 2007
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Not sure there is an optimal rate as it all depends on volume / fish load / amount of media in the filter. It would be a hard thing to throw a random number on and be correct.
 
J

justin guest

Feeder Fish
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Jun 6, 2008
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I have to agree. one trial i know of showed that the nitrifying capacity of a filter increases with flow rate. in this trial the upper limit wasn´t reached because the maximum flow rate used was thought to be well above a useful average. This also fits to my practical experience of water flow rates in filters. Whether you should be using higher flow rates just for this reason is questionable though. Of course higher flow rates for instance in trickle filters also means more oxygen in your system but the down side is a reduction of fine particle filtration eficiency. To get around this problem you need a larger mechanical filter surface area. You see there are pros and cons no matter what you do. Getting back to your question though don´t worry too much about the ideal flow rate for bacteria in your filter (they also do well at lower flow rates), just make sure the filter is big enough to cope with the mechanical filtration necessary for your system and use a biological filter material with a good surface area. As a rough guide always buy a filter at least one or two sizes larger than the manufacturer recommends. That way you´re on the safe side when your fish start growing a bit. And extremely important make sure you get enough oxygen in the system, for instance with an air pump if using canister systems.
Good luck
 
B

brianp

Candiru
MFK Member
Oct 5, 2007
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With the average filter filled with media, regardless of the filter type, you should have no concern other than the flowrate being impeded too much by the accumulation of debris. Any biomedia bed will generate sufficient turbulence to allow the water to make contact which sufficient surface area to remove nitrogenous contaminants. Once the water is moved into the filtration media by the pump, the only force driving the uptake of, say ammonia by the bacteria is "diffusion". Diffusion is dependent upon two factors.....temperature (a constant, more or less) and the steepness of the diffusion gradient. The steeper the gradient, the faster the uptake. The gradient steepness is dependent upon the rate at which new, contaminated water is brought into the filter and the rate at which the bacteria are assimilating the nitrogenous waste molecules. The rate of bacterial assimilation will be controlled primarily by the amount of oxygen the bacteria receive. This means the following:
1. You should not deliberately invoke measures to reduce the flowrate through your filter.
2. Service your mechanical media routinely to prevent the flow from being impeded.
 
H

Hawkfish3.0

Piranha
MFK Member
Feb 19, 2007
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Excellent answer!!
 
A

ar0wan

Epistemologist
MFK Member
May 4, 2007
1,288
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right on! It can be too slow, but [in all practicallity] can never be too fast.
In order to starve them out, you'd have to completely deplete your tank of all waste.
step #3 - get more fish
 
F

FireMedic

Plecostomus
MFK Member
Dec 13, 2007
805
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Middle of somewhere, Oulu Wisconsin
brianp;1866668; said:
With the average filter filled with media, regardless of the filter type, you should have no concern other than the flowrate being impeded too much by the accumulation of debris. Any biomedia bed will generate sufficient turbulence to allow the water to make contact which sufficient surface area to remove nitrogenous contaminants. Once the water is moved into the filtration media by the pump, the only force driving the uptake of, say ammonia by the bacteria is "diffusion". Diffusion is dependent upon two factors.....temperature (a constant, more or less) and the steepness of the diffusion gradient. The steeper the gradient, the faster the uptake. The gradient steepness is dependent upon the rate at which new, contaminated water is brought into the filter and the rate at which the bacteria are assimilating the nitrogenous waste molecules. The rate of bacterial assimilation will be controlled primarily by the amount of oxygen the bacteria receive. This means the following:
1. You should not deliberately invoke measures to reduce the flowrate through your filter.
2. Service your mechanical media routinely to prevent the flow from being impeded.
Click to expand...
This and justins pretty much sum it up.
 
U

USMCtanker

Feeder Fish
MFK Member
Dec 9, 2005
4,175
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wa
brianp;1866668; said:
With the average filter filled with media, regardless of the filter type, you should have no concern other than the flowrate being impeded too much by the accumulation of debris. Any biomedia bed will generate sufficient turbulence to allow the water to make contact which sufficient surface area to remove nitrogenous contaminants. Once the water is moved into the filtration media by the pump, the only force driving the uptake of, say ammonia by the bacteria is "diffusion". Diffusion is dependent upon two factors.....temperature (a constant, more or less) and the steepness of the diffusion gradient. The steeper the gradient, the faster the uptake. The gradient steepness is dependent upon the rate at which new, contaminated water is brought into the filter and the rate at which the bacteria are assimilating the nitrogenous waste molecules. The rate of bacterial assimilation will be controlled primarily by the amount of oxygen the bacteria receive. This means the following:
1. You should not deliberately invoke measures to reduce the flowrate through your filter.
2. Service your mechanical media routinely to prevent the flow from being impeded.
Click to expand...
:iagree:
 
Nic

Nic

Peacock Bass
MFK Member
Oct 8, 2005
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FireMedic;1867926; said:
This and justins pretty much sum it up.
Click to expand...
what he said ^ :)
 
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