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filter bacteria in a low-tech tank

jlm

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22 Jun 2009
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Before jumping in the El Natural wagon, and after reading all the related forums in the ukaps web, I have two major doubts about this system:

1 - Given that a biological filter (ie bacteria) isn't necessary and can even be counterproductive since it 'steals' nutrients from the plants, but considering that the filter would need to be running anyway to provide some water flow - preferably with some filtering material in it to retain the thicker particles - wouldn't bacteria become a problem when they eventually grow in the filter material over time, as they probably will? Would it be a case of getting rid of them on a regular basis, cleaning the filter thoroughly etc?

2 - The potting compound recommended as substrate will eventually exhaust itself in 6-12 months. Would it need replacing with fresh potting compound, or perhaps the thing to do then would be to add fertilizers to the water column instead? Would the fish produce be enough to sustain the plants, once the substrate is finished?

3 - This may be a far-fetched idea, but could crushed egg shells be used instead of the oyster shells that are sometimes recommended for mixing with the substrate?

Any ideas will be very welcome indeed.
 

ceg4048

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jlm said:
Before jumping in the El Natural wagon, and after reading all the related forums in the ukaps web, I have two major doubts about this system:

1 - Given that a biological filter (ie bacteria) isn't necessary and can even be counterproductive since it 'steals' nutrients from the plants, but considering that the filter would need to be running anyway to provide some water flow - preferably with some filtering material in it to retain the thicker particles - wouldn't bacteria become a problem when they eventually grow in the filter material over time, as they probably will? Would it be a case of getting rid of them on a regular basis, cleaning the filter thoroughly etc?
Hi, I can't imagine that you have read this on UKAPS. This concept is completely false. There is no way that filtration steals nutrients from plants. Just the opposite in fact. The output of filter bacteria is nitrate which is critical for plants use as an important source of Nitrogen. So there is no way filters can be blamed for nutrient theft.

jlm said:
2 - The potting compound recommended as substrate will eventually exhaust itself in 6-12 months. Would it need replacing with fresh potting compound, or perhaps the thing to do then would be to add fertilizers to the water column instead? Would the fish produce be enough to sustain the plants, once the substrate is finished?
All enriched sediments ultimately lose their enrichment over time. In a high tech tank this might take 6 months or so. In a low tech tank it will last longer due to the lower nutrient uptake rate. However, this is replaced by the organic waste buildup in the sediment and the subsequent nitrification and other types of recycling that occurs in the sediment due to bacteria. Stop flogging bacteria. They are what make your tank function.

jlm said:
3 - This may be a far-fetched idea, but could crushed egg shells be used instead of the oyster shells that are sometimes recommended for mixing with the substrate?
Well, I agree this is certainly far fetched. Use a quality substrate such as Aquasoil and abandon these other ideas because they are simply not valid.

In a non carbon enriched low tech tank the standard procedure is to avoid water changes, avoid high intensity lighting and to dose the water column with small amounts of inorganic fertilizers once or twice a week.

Cheers,
 

jlm

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Thanks for your reply, ceg4048. I can't be sure where I have read this about filter bacteria, I have been doing quite a bit of research in the last couple of days and it's been many different webs that I've visited. But I recall that Diana Walstad's original setup was for no filter whatsoever, only water flow, although she later changed her mind about this.

The question remains, however, is the filter in a El Natural tank to be treated the same way as a high-tech one? Isn't there a risk that some of the stuff retained by the filter (biological or otherwise) can be useful for the plants, such as the ammonia?

I am a total novice in low-tech aquaria (and in fish-keeping in general), as you can tell, and I am trying to decide which set up to go for in a new 180/240 liter tank.
 

ceg4048

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Well, it's entirely possible to run a filter-less low tech planted tank, but one needs to understand the mechanism before drawing the conclusions of why this is possible and what it's implications are.

First of all, bacteria won't disappear just because there is no filter. They are everywhere - in the water, in the substrate and on all submerged surface. A byproduct of photosynthesis is oxygen production. Plants have a symbiotic relationship with certain bacteria and oxygen production stimulates, and enhances these specific bacterial populations whether they be in filters or elsewhere in the tank.

The particular bacteria of interest are in the group we commonly call "Nitrifying Bacteria". There are two basic sub-groups.
1. A group that consumes Ammonia which includes species such as the waterborne Nitrosomonas, Nitrosococcus and the sediment species Nitrospira. These convert Ammonia into Nitrite (NO2).

2. A group that consumes Nitrite (NO2) such as Nitrobacter as well as Nitrospira. These convert Nitrite into Nitrate (NO3). This is referred to as the Nitrogen Cycle or Nitrification.

These two groups work in unison to basically detoxify ammonia, which is constantly being produced by decaying organic cells into the much less toxic Nitrate. Plants consume both Ammonia and Nitrate directly in order to obtain the much needed Nitrogen. Now, filter media works by housing extra quantities of both groups of bacteria so they would compete with ammonia uptake by the plants, but so what? Ultimately their byproduct is Nitrate so that the Nitrogen in the form of NH4 that the bacteria "steal" from the plants is preserved. It does not disappear from the system but instead is returned to the plants in a less obnoxious form, albeit a little slower. Since NH4 is extremely toxic it's a much better idea to have as many organisms as possible consume this toxin immediately. There is no point whatsoever in deleting a filter in a low tech tank because as you yourself realize there are other benefits such as water circulation and detritus/particle collection that plants cannot perform - so there is an aesthetic imperative as well. This does not mean that filterless is impossible and I'm not arguing against the D. Walstead principles, I'm just saying why bother? There is little advantage. Growth can be advanced by adding small quantities of inorganic fertilizer to supplement the organic cycle.

If you want to delete something from a low tech tank then delete the water changes. That's a much better benefit because this keeps the CO2 levels stable which serves the plants needs.

Cheers,
 

jlm

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Right. When you say 'There is no point whatsoever in deleting a filter in a low tech tank', I imagine you'll agree that chemical filtration in the form of carbon (the usual) will remove beneficial compounds and fertilizers needed by plants, so one should as a precautionary measure remove the carbon from the standard filter. This of course does not apply to mechanical and biological filtration, which are a useful form of back-up filtration in a planted tank, as you discuss.

Regarding the inorganic fertilizer that can be added to encourage growth - when the subsoil gets exhausted, or even with fresh subsoil - would off-the-shelf water column ferts such as Seachem, Tropica or Greg Watson do? Or even tablets directly to the soil...

Thanks for your reply
 

ceg4048

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Well, activated carbon has a bad rap sheet and it's entirely undeserved. So what if it removes some nutrients? Just add more nutrients... end of trouble.

Activated carbon helps to remove discolouration and other organic/inorganic toxins so it's benefits can be worth more than whatever trouble it causes. On the other hand, activated carbon is not a necessity either so if you remove it it not really a big deal. In other words, activated carbon won't make or break your tank so there is really no need to fret about it one way or the other.

Well why wait for sediment to get exhausted? Here is the thing that I'm finding newcomers to plants have trouble grasping; Submerged aquatic plants have a higher capacity to uptake nutrients through their leaves than from their roots. This is the basis of their success, because many of them are rooted in extremely poor soil to begin with. In fact, in their natural habitat you'll find that most tropical jungles are not very sediment rich. Most of the nutrients in these environments are tied up in the foliage that falls off the trees, and so feeding takes place in the upper few inches of the sediment. This includes huge mahogany and fig trees which dominate the landscape. When the rain forest floods in the wet season, nutrients fill the water column from the leaf litter as it's flooded making it accessible to the inundated plants.

Foliar uptake is the key to survival, so it's best not to think about these plants in the same way as terrestrial or potted plants. Our plants are much more talented, so there is no need to get tunnel vision regarding sediment. It's alays nice to have a rich sediment, but people focus too much on optimizing sediment and they lose the big picture.

Let me show you an example; The plant in the foreground of this picture has never seen sediment. It's growing on top of an ornament. The plants in the background are growing in an inert sediment. I didn't ever have to think about sediments because I dose the water column heavily. I simply don't care about exhaustion because no soil can match the effectiveness of water column feeding, but again, its better to have a rich sediment than to not have it since the plants feed from both sources.
8394125871_31a140938f_c.jpg

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Sure you can buy off the shelf ferts, but why bother? They only cost 100X more than they need to. if you intend to run a non-injected tanks the your fish will supply the bulk of Nitrogen and Phosphorous in the water column via urine. Their faeces will penetrate the sediment and decay there where bacteria will fix the Nitrogen for the roots. Any organic material that decays will feed the plants/bacteria who will then recycle the toxic components. So the sediment never really gets exhausted, it just declines from rich to normal. Inorganic salts such as KNO3 (Potassium Nitrate) and KH2PO4 (Potassium Phosphate) dosed in the water column once a week or so will be of tremendous benefit. I'd just get them from Greg Watson (if you are in the USA, from our sponsors in you live in Europe) but, if you feel more comfortable buying commercially then Tropica's TPN+ would be the way to go since it is an all-in-one liquid.

Cheers,
 

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