On media, filtration and bacteria

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UNC-CH created the topic: On media, filtration and bacteria

While looking at all the different types of biomedia to fill my filstar, I stumbled upon a lot of info regarding different types of media, their uses, and filtration which has me asking questions I had never really been concerned with before. :huh:

First is the issue of very porous media such as biohome. The people that make and/or sell this claim that because of it's deep porous structure it houses anaeobic bacteria which will reduce your nitrates. I never took these kinds of claims seriously but I thought I'd ask to see if there was any truth to such claims.

The second is related to the first in that this media, a newer and improved version of K1, is made by the same people. It is completely different from porous media in that it is comparatively smooth. They claim that this media (let's just use K1 for the purpose of this question) is very effective in a moving bed filter. This is because in a moving bed filter the media are constantly banging together and releasing bacteria into the water which then quickly converts ammonia into nitrite into nitrate. But because this media is not porous your nitrate levels will quickly rise when used in a moving bed filter. Are moving bed filters efficient? I had assumed that bacteria needed a porous surface to grow on which is why ceramics are used, but this suggests that it grows just as well on smooth plastic (although it does contain a lot of surface area).

I began to wonder about the life-span of nitryfying bacteria ... what happens when it dies? ... how long does it live? does it need to be cleaned off the media or is it consumed by other newer bacteria? ... too many questions without answers. :pinch:
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Lammergeier replied the topic: On media, filtration and bacteria

I'll try my hand at answering a few of these... :laugh:

Porous structure = houses anaerobic bacteria which will reduce nitrates: I doubt it. In any filter (and with any bio media) there may be small oxygen deficient areas where nitrate-reducing bacteria can grow, but the concentration of bacteria would be way too small to make much of an impact.

I've never heard of a moving bed filter but I don't think knocking the bacteria into the water constantly would make it convert ammonia at a faster rate.

Bacteria doesn't need a porous surface to grow on, but the amount of bacteria in your filter is limited by the available surface area. More porous bio media = more surface area = more bacteria = faster ammonia/nitrite removal.

I'm not sure how long an individual bacterium lives, but in a well-established filter there will be a steady rate of new bacteria growth and old bacteria die-off, keeping the overall concentration of nitrifying bacteria in the filter (roughly) the same. The nitrifying bacteria won't consume the old, but like in any biological system there will be a bunch of other bacteria species present that would. Chances are that some of that stuff would still end up being a part of the waste that accumulates in a filter that eventually needs to be cleaned though.
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Goranothos replied the topic: On media, filtration and bacteria

Lam's post was spot on, IMO.

UNC, I wouldn't obsess about biomedia. What you want in biomedia is lots of surface area for the bacteria to cling to. If, for some reason, ceramic noodles tend to disintegrate in your filters, then there are always good old plastic pot scrubbers and/or coarse sponges. No need to overthink this.

The main thing to remember about biomedia is not to clean it with chlorine water (i.e. tap water for most of us).

:)

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Poseidon2.0 replied the topic: On media, filtration and bacteria

UNC-CH wrote: First is the issue of very porous media such as biohome. The people that make and/or sell this claim that because of it's deep porous structure it houses anaeobic bacteria which will reduce your nitrates. I never took these kinds of claims seriously but I thought I'd ask to see if there was any truth to such claims.


I have asked similar questions here and not received an answer before. I would only note that it isn't a claim that is unique to the biohome people. I have read about the phenomenon of reducing nitrates and cohabitation of aerobic and anaerobic bacteria in lava rock, which is used a lot in koi pond filters. In fact, it is the "Pond guru" (out of the UK) that developed the biohome idea out of this fairly widespread idea among pond people regarding lava rock. Eheim use to sell lava rock in their canister filters, once upon a time.

I am not sure how well this works or not. The claim is that it takes six months to develop the anaerobic bacteria and only one of my filters is that old.

Lamm may well be right that the amount developing is very small and/or has a negligible effect on nitrates or that perhaps you would need such massive amounts that would make it impractical. I am not sure. It would be good to try and test it (which I am doing in my limited way). Would still like to read something more that doesn't come from someone shilling a product. A hard thing to test though without a lab I think. I have been happy with the results of using the biohome, though, apart from this.

In any event, adding pothos filters will like be a faster way to deal with the nitrates. Still mean to put up a post about mine (i.e., pothos filters) soon!
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Poseidon2.0 replied the topic: On media, filtration and bacteria

Hey there Lamm. I see that you are moving up in the world!

Happy moderating! B)
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UNC-CH replied the topic: On media, filtration and bacteria

Ah! Porous media = more surface area = more room for bacteria to grow. This explains a lot. For some reason, I had always assumed that bacteria needed a rough surface to 'hold on' to and wouldn't do so well on something smooth like plastic. I have a large bag of blue bio balls that I've never used because I had always wondered how bacteria could ever grow on them. Now I understand that it's just about surface area. Looking back, I don't know why I ever thought that the actual surface mattered.

@goranothos - you can tell I'm obsessing about this? :) Good advice. Now that I understand things the way you and Lamm explained it, there's nothing left to think about though.

@posiedon - I think they're just trying to sell their media with claims that it reduces nitrate. I agree that some anaerobic bacteria might grow in that media but probably much more would be needed to have the impact on nitrates that just one pothos plant would have.
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Goranothos replied the topic: On media, filtration and bacteria

Hold on now. I certainly don't want to contradict Rocksor. He claims that the smooth plastic "bio balls" are best used in a wet/dry sump, and I believe him. He has also stated that the plastic pot scrubbers are good in a closed system such as a canister filter.

Again, don't obsess. For a canister filter, plastic pot scrubbers and/or coarse filter sponges make great choices for bio media, especially if you have had problems with ceramic media.


Now, please bear with me as I get on my "nitrate" soapbox.

We all know that the end result of conventional aquarium filtration methods is nitrate buildup.

Now that Captain Obvious has done his job, let's review the best known ways to reduce nitrates in our fish tanks.

(1) Water Changes

(2) Plant Based Nitrate Filters (aquaponics)

(3) Anaerobic Nitrate Filters (denitrators)

(4) Resins and other chemical nitrate absorbers


I have a feeling that I may be getting in over my head here. Perhaps we should consider doing a forum article on this subject?

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Lammergeier replied the topic: On media, filtration and bacteria

There needs to be a 'summon Rocksor' button on here!
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UNC-CH replied the topic: On media, filtration and bacteria

By the way, instead of pot-scrubbers I would think these would do just as well? I have plenty of these ... but I think pot-scrubbers have a sponge in the middle ... these don't. Still, I think they are basically the same.

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Lammergeier replied the topic: On media, filtration and bacteria

I've read those aren't nearly as good as pot scrubbers. I'll try and find the link for you.

Edit: Actually check the sticky by Rocksor at the top of this forum. I think MFK is down but when it's up that link is what I was referring to.
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