Gravel vaccuuming and bio-filter

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99RedSi

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Dec 2, 2002
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I was wondering if gravel vacuuming your tank with a syphon/python disrupts or even possibly destroys (if taken too far) the beneficial biological bacteria in the gravel?

Or maybe I'm way off?
 

ArkyLady

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Nov 27, 2002
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From what I've read, the bacteria will be securly attached to the gravel and you shouldn't be able to dislodge enough of it to harm your bio filter.
 

FishBait

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Agreed, you will inevitably remove some of your bacteria, but not enough to cause any significant loss. Of course if you are worried about it, you could always do the 1/2 gravel method, where you only siphon half of it at a time.
 

Hammerman

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Oct 2, 2002
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Originally posted by ArkyLady
From what I've read, the bacteria will be securly attached to the gravel and you shouldn't be able to dislodge enough of it to harm your bio filter.
Originally posted by FishBait Agreed, you will inevitably remove some of your bacteria, but not enough to cause any significant loss. Of course if you are worried about it, you could always do the 1/2 gravel method, where you only siphon half of it at a time.
I agree with both ArkyLady, and Fishbait... You shouldn't have an issue.
 

RTR

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Oct 5, 1998
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Agree w/ewok. Smothering the biofilms with mulm is harder on the bacteria than vacuuming. Consider the case of fluidized bed filters - they are effectively being vacuumed 24/7/365 and function as nitrification devices.
 

wetmanNY

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My fears that bacteria were ground off gravel surfaces used to be exaggerated, until calmed by RTR's point about fluidized bed filters. I still think a floc of humus the same size as a grain of gravel offers enormously greater microzones for bacteria.

I prefer to leave the microhabitats of facultative bacteria that can switch between aerobic and anaerobic metabolisms-- and maybe even some obligate anaerobes-- to develop in peace, oxidizing any sulfides to harmless sulfates, creating acidic low-oxygen microzones where the iron in my substrates is ferrous and available to plant roots, maybe even giving me some de-nitrification (my nitrates typically run <10ppm). Besides, my older (5 or 6 year) substrates are probably quite laden with phosphates by now.

I keep reading "algae problems" threads in all the forums that reinforce my impression that algae problems are related to: overwashed "aquarium" gravel with no humus "crud"or silt, substrate disturbance and a snowstorm of flake feed. My tanks have many kinds of algae in them, but not much of any one kind.

Gravel-digging roles are taken up by Melania snails and Botia modesta hunting for them like truffle dogs, since I don't have any big earth-shifting Cichlids.

How would "crud" work its way down into the substrate if the fishkeeper didn't stir it all in, from time to time? What happens to detritus below the surface: doesn't it break down pretty completely, leaving only some dark "humus."

You see, there is a successful different way...
 

RTR

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That mulm, at full digestion, is very fine particulate, close to an organic clay. It does not take hobbyist intervention to get it to sift down between the gravel grains. For planted tanks within reason it is great nutrient reservoir. Unfortunately for FO tanks it is the same, and IMHO is more likely to result in algae issues than not. For FO, I'll stick with routinely full-depth vac'd substrates and low nitrate and phosphate water columns. For planted tanks I'll leave it in place, and get low nitrate and phosphate water columns by the action of the plants.

There is one caveat here which we have ignored - if the substrate has been ignored itself for long periods, the nitrifiers (and other aerobes) will have been suffocated on the gravel particles and have migrated into the mulm. Massive cleanup of this after long neglect is likely to affect the bacterial colonies/biofilms.
 
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