# would i be right in saying?...



## Mark Evans (8 Dec 2010)

I've been thinking this for sometime, and i'm a bit curious. 

Clive/Darrel

If you had 2 filters running...lets say for arguments sake,1 is 1700LPH and the other is 1000LPH. Would the filter of a lower turnover become the strongest for bacteria growth? Is the water in the filter for a slightly longer time?

or if you had a filter like an eheim, which could have the flow 'regulated' on a 'slow' setting the ammonia and the likes would be 'digested' quicker, due to it passing through filter slower?

so in my mind, maybe a high and low turnover filtration system would be good?


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## Tom (8 Dec 2010)

I would imagine you'd also have to consider the O2 requirement. I'm not sure of the O2 uptake rates of bacteria, but presumably if you have too low a turnover, you would start to limit bacteria growth as O2 would be stripped. It's probably a case of finding the medium, and for all I know it's effect may only be minimal!

What would be the benefit of running 2 different speeds simultaneously, if the theory is correct? Could the same effect be achieved by keeping the flow rate the same, but increasing the filter capacity so the water is in contact with media for longer?


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## Garuf (8 Dec 2010)

I think o2 levels would be your clincher as Tom states. I've been reading with great interest that Tom Barr is now using the much maligned wet/dry filters because of the increased levels of o2, while increasing biological capacity and co2 capacity without endangering live stock.
Surely the speed of a filter is relative to the size of the tank, therfore it should be chartable to estabis what filter would be best for purpose?


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## ceg4048 (8 Dec 2010)

Well I think it's an oversimplification to use flow as the only parameter. There are so many variables which interact, you could really wrap yourself around the axle. As stated, O2 availability is a key factor since these are aerobic bacteria. But there are also other requirements. Most people only consider Ammonia and Oxygen when thinking about these bacteria but in fact, nitrification takes a lot more than just these two chemicals. For example, some bacteria also consume organic Carbon. That's why adding peat and mulm to a filter bed or to the sediment helps bacteria. The bacteria that obtain their Carbon from organic sources such as peat are called heterotrophic. Some nitrifying bacteria are autotrophic, which means that they obtain their carbon from inorganic sources - like CO2. In order to produce energy, bacteria also need PO4, Magnesium and Iron.

In a planted tank these factors are significant, and we shouldn't forget that a "waste" product of photosynthesis is Oxygen. So if we are dumping all these components into the water it may easily be that the flow rate in the tank from that standpoint becomes less relevant simply because of the possibility that bacteria are being presented with an unlimited supply of all these components from their point of view. Therefore if I've saturated the water with O2/CO2 does it really matter to the bacteria whether I have high flow or low flow? They are still presented with an infinite Oxygen/CO2 rich environment. The microbe limiting components for a healthy, stable planted tank is more likely to be the Ammonia itself because healthy plants will compete with bacteria for this resource. If this is the case then what are we worried about? Limited Ammonia? That sounds like an awfully nice problem to have, in which case I don't have to try to figure out whether I need a combination of high flow and low flow, or which is better in this environment.

At some point, there is a minimum required flow, below which the bacteria are not producing enough nitrification. If the filter is clogged with detritus for example, this is a classic case where flow is blocked, which stifles Oxygen availability. The detritus breaks down and releases ammonia which goes unprocessed. When ejected into the water column this can lead to some forms of algae.

Since we really don't have measurement showing what flow rate through a filter, in what tank, produces what level of nitrification, it's a very tall order to compare the effectiveness of one filter rating versus another in a given tank. I can't find the link right now, but I recall an Ammonia pull-down test done by a discus club. The combatants were a 1700LPH Eheim 2180 versus a 2300LPH Fluval FX5. The Eheim smacked down the FX5 significantly, even with the lower rated flow. Why? Simple. The 2180 has a bigger bucket and therefore a much higher media capacity so in this particular case the lower flow rate was trumped by higher bacterial population. Does this imply that a lower flow rate is better than a higher flow rate through a filter? Hardly. That test was in a bare tank with kitchen ammonia being tossed in the tank. In a normal planted tank, would there be as significant a difference? Hard to say, because the conditions and the dynamics would be totally different.

If I have a choice in a tank to have multiple filters, I'm goin' for the two biggest, baddest filters possible, with as much flow rating as possible simply because I'm a flow/distribution lunatic. And that flow rate is gonna be more useful to me in terms of nutrient/CO2 distribution, and will solve a hell of a lot more problems than what I could measure in terms of nitrification.  

Cheers,


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## Mark Evans (9 Dec 2010)

ceg4048 said:
			
		

> The Eheim smacked down the FX5 significantly, even with the lower rated flow. Why? Simple. The 2180 has a bigger bucket and therefore a much higher media capacity so in this particular case the lower flow rate was trumped by higher bacterial population.





			
				Tom said:
			
		

> Could the same effect be achieved by keeping the flow rate the same, but increasing the filter capacity so the water is in contact with media for longer?



these wre the bits i forgot to add. It's actually answered my question now   

OK, another question....

if bacteria in a filter requires oxygen, on startup of a new tank, it's limited right? we then bang loads of co2 in the day starving the filter. At night bacteria grows. whats the process of good strong filter bacteria?...on startup that is.


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## roadmaster (9 Dec 2010)

I am with Clive if he don't mind. Have always been  a two filter guy and the more flow the better.
Now if UV sterilization was a factor ,then the lower flow would be beneficial for it would allow more contact time with UV bulb .But that perhaps is an altogether different animal.
I have long theorized ,that bacteria can develop a bit quicker in wet dry, or hang on the back filter's due to increased oxygen available as opposed to sealed canister filter, though I could offer little convincing evidence other than observations to those who poo pooed the notion. But the larger surface area for bacteria in canister filter's  media is considerably more than that offered in nearly all HOB filters and flow is often more as well.
Flow for me,,is all important unless fishes would fair better with less.


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## roadmaster (9 Dec 2010)

Mark Evans said:
			
		

> ceg4048 said:
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Would assume that when CO2 is offered,that plant mass is there to receive it.Plant's produce oxygen during the day .


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## ceg4048 (9 Dec 2010)

Mark Evans said:
			
		

> ...if bacteria in a filter requires oxygen, on startup of a new tank, it's limited right? we then bang loads of co2 in the day starving the filter. At night bacteria grows. whats the process of good strong filter bacteria?...on startup that is....


Mmm...I don't think this is quite accurate mate. Lets break down the scenario in small steps:
At tank startup your bacterial population is low, so they are seeing at least the equilibrium O2 levels in the tank and don't have an appreciable affect on the O2 consumption.

Again, you have plants in the tank producing O2. There ought not to be any O2 limitation but there might be some NH4 limitation. At night the O2 values drop, but do they drop to limiting values? Unclear.

The dissolved CO2 concentration in the water has absolutely nothing to do with the ability of Oxygen to dissolve in the water. The two solutes have nothing to do with each other. This is a fundamental principle that perhaps folks are confused about. The ability of O2 to dissolve in water is limited only by its partial pressure of the gas and the temperature of the water. The solubility of O2 and it's availability to the bacteria is not affected at all by the presence of high levels of CO2, even though the CO2 has a 10X higher solubility. 

As I mentioned before, some bacteria actually use CO2, so high CO2 levels are a boon to them. The indirect affect of CO2 in the water column is actually the reverse of what you've just stated. The plant uses the CO2 and pumps more O2 into the water column. People seem to have difficulty getting to grips with this. In an unplanted tank O2 may be at limiting values, but we don't have to worry about that at all - as long as the plants are healthy.

Bacteria grow all the time, not just at night. In fact it's highly likely that there populations will grow faster during the day since there is a high O2 and CO2 level. Who says bacteria only grow at night? There is no light dependency except for those bacteria like BGA which are phototrophic, in which case they definitely grow more during the day and suffer at night.

The best way to get your bacterial colonies going at startup (or any time for that matter) is to do all the thing for healthy plants. The relationship between plants and nitrifying bacteria is a tightly woven symbiosis. Whatever is good for plants is also good for bacteria. Good flow, high CO2, plenty of nutrients and good maintenance practices. The better the plants do, the better the bacteria do. There is no magic and there is really no way to speed things up other than to seed the filter and sediment with mulm. The population follows a logarithmic pattern 1-2-4-8-16....

All those mad scientists who dump loads of ammonia in the tank think they are doing the right thing, but they are actually killing their own bacterial populations with toxic levels of ammonia.

Cheers,


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## Mark Evans (9 Dec 2010)

Thanks clive. copied and saved


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