Why filter?

dw1305

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Hi all,
Welcome, nice tank.
.......but it’s really only suited to small rather shallow aquaria.
If I wanted to go even lower maintenance I'd go for a wide shallow tank with a large surface area to volume ratio, the advantage of this is that a larger gas exchange surface means quicker diffusion of CO2 and oxygen both in and out. I think tank architecture is part of the reason why "BigTom's" "Bucket of Mud" has been so successful, and if you read through his journal <Tom's Bucket O' Mud - new vid page 28 | UK Aquatic Plant Society> you can see it is an absolute triumph.
Have a look at the links from <"Low tech. lighting levels....">.
I recently turned off the power filter on a very long established tank. (1995) Just replacing it with a very small powerhead for gentle circulation. What I’ve found really interesting, is that almost immediately the plants responded. It was almost like an on switch.
Can I ask what media was in the filter? And is there any possibility that anaerobic denitrification may have been occurring?

cheers Darrel
 

Affinis

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Thanks for the Reply Darrel,

The tank is an old Juwel 180 and was running a rather oversized Eheim 2217 containing just coarse foams. I was interested to see if an oversized filter would indeed create conditions for anaerobic denitrification to take place, subsequently I’d deliberately not touched the filter for the ten months it was in action. To my surprise the tank has been slowly building nitrate over this period, something which hasn’t really occurred over the 24 years this tank has been set up. In fact the main reason I’ve now decided to turn it off, is to see if the nitrate accumulation will actually drop back down naturally. I should add that the only nutrient export this tank has is from the removal of excess plant material.
 

Soilwork

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Thanks for the Reply Darrel,

The tank is an old Juwel 180 and was running a rather oversized Eheim 2217 containing just coarse foams. I was interested to see if an oversized filter would indeed create conditions for anaerobic denitrification to take place, subsequently I’d deliberately not touched the filter for the ten months it was in action. To my surprise the tank has been slowly building nitrate over this period, something which hasn’t really occurred over the 24 years this tank has been set up. In fact the main reason I’ve now decided to turn it off, is to see if the nitrate accumulation will actually drop back down naturally. I should add that the only nutrient export this tank has is from the removal of excess plant material.

Hi Affinis

Did you notice any other changes to anything at all with the tank during those 10 months other than accumulation of nitrate?

What is the TDS in this tank? Any change in the 10 months?

Lastly, do you have any pictures of the 180?

Regards

CJ
 

dw1305

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Hi all,
I should add that the only nutrient export this tank has is from the removal of excess plant material.
To my surprise the tank has been slowly building nitrate over this period, something which hasn’t really occurred over the 24 years this tank has been set up.
That is strange, it may be to do with the lack of water changes. This could have led to a deficiency of one of the other <"essential nutrients">.

Personally I don't often measure NO3, it is <"more problematic"> than most forums acknowledge.
What is the TDS in this tank? Any change in the 10 months?
That is the next question for me as well, did you measure the change in conductivity (TDS) during the 10 months?

cheers Darrel
 

Soilwork

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Hi all, That is strange, it may be to do with the lack of water changes. This could have led to a deficiency of one of the other <"essential nutrients">.

Personally I don't often measure NO3, it is <"more problematic"> than most forums acknowledge.That is the next question for me as well, did you measure the change in conductivity (TDS) during the 10 months?

cheers Darrel

Hi Darrel.

Could it simply not be that a large filter such as the 2217 is encouraging nitrification because the flow takes the ammonia production directly through the media?

I’m not questioning that their would be equal quantities of microbes in certain areas of the tank but it would make sense that the most nitrification would take place at the media site because it is quickly and constantly being taken there. In the case of high flow rates and filter material surely this is removing some of the plants access to ammonia. That would be my hypothesis on why there was an almost immediate response to the filter being removed and why they may use more oxygen. This brings me personally back to my original question. Why filter? Maybe most people just haven’t tried it this way as a test.
 

Affinis

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The tank has been ticking along nicely over this period, zero algae for example, but plant growth hasn’t been as fast as in previous years. It’s obviously been running rather lean, even the duckweed had become very small and was hardly growing.

Over this period the TDS has dropped slightly from around 400, to 342 today, but this is no surprise because I’ve only been using rainwater for top up since Xmas. Evaporation is minimal on my tanks because they’re well covered and not heated.

The last water change on this tank was 50% Xmas 2017, and previous to that five years earlier. It’s probably only had a handful of water changes since 1995.

Another thing I’ve noticed since I turned off the filter, is that the TDS is now falling much faster. But I guess that’s down to the marked increase in plant growth.

As you can see it’s not a highly manicured tank, most of the plants are the originals from 1995. I really just let it do it’s own thing, and just pull out excess when it becomes too chaotic. Sorry rather poor iPad pic.
 

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dw1305

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Hi all,
Could it simply not be that a large filter such as the 2217 is encouraging nitrification because the flow takes the ammonia production directly through the media?........ In the case of high flow rates and filter material surely this is removing some of the plants access to ammonia.
Yes certainly could be, if you have plenty of oxygen in the filter then conditions will be suitable for nitrification to occur.

The volume of the filter is actually relatively unimportant, oxygen (so flow in this case) is the really important metric. You just don't need a huge volume of filter media to support nitrification. If you think of the <"rotating arm trickle beds">, or <"rotating contactors">, at older style sewage treatment they cover a relatively small area.

It is quite difficult to quantify exactly where the ammonia is being oxidised, you could measure it quantitatively via <"isotopically labeled tracers ([15N]ammonium to [15N]nitrate)">, but I'm not aware of any research that has looked at planted aquariums.

There are some <"mesocosm studies"> in constructed wetlands. This from the linked paper
Each system was dosed with a single pulse of 15N ammonium mixed into the feed wastewater, and the fate and transport of the isotopic nitrogen were determined. The 15N pulses took 120 days to clear the heavily loaded field-scale wetlands. During this period small reductions in 15N were attributable to nitrification/denitrification, and a larger reduction due to plant uptake. Mesocosm tests ran for 24 days, during which only 1–16% of the tracer exited with water, increasing with N loading. Very little tracer gas emission was found (∼1%). The majority of the tracer was found in plants (6–48%) and sediments (28–37%). These results indicated a rapid absorption of ammonium into a large sediment storage pool, of which only a small proportion was denitrified during the period of the experiment. Plant uptake claimed a fraction of the ammonium, determined mainly by the plants requirement for growth rather than the magnitude of the nitrogen supply.
As you can see it’s not a highly manicured tank, most of the plants are the originals from 1995. I really just let it do it’s own thing, and just pull out excess when it becomes too chaotic.
Perfect, plant growth still looks pretty good.
Another thing I’ve noticed since I turned off the filter, is that the TDS is now falling much faster.
I'm not sure about that, but I can't think of any other reason.

Keep up the good work.

cheers Darrel
 

Affinis

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Thanks Darrel,

I’ll keep an eye on things, and report back in a few months.

At the moment my intention is to let the TDS slowly drop. But I haven’t decided how far to let it go, before I go back to using tap water for top up. Being in Essex, I’m not used to dealing lower levels, although I do have one experimental tank that’s currently running at a TDS of just 12.
 

Soilwork

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Thanks Darrel,

I’ll keep an eye on things, and report back in a few months.

At the moment my intention is to let the TDS slowly drop. But I haven’t decided how far to let it go, before I go back to using tap water for top up. Being in Essex, I’m not used to dealing lower levels, although I do have one experimental tank that’s currently running at a TDS of just 12.

Hi Affinis,

How is the low TDS tank doing and how does it compare to the 180?

Cheers
CJ
 

Affinis

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Hi Soilwork

My low TDS tank is just an experiment really. I’d rather neglected it during the summer, so it’s a bit of a mess currently.
I was playing around with zero flow, but I’ve had a cyano issue, so I’ve recently put a very small circulation pump back in.
On the plus side the Salvinia and Ambulia grow like crazy and the water quality is amazing.

Although the tank is very untidy it grows just as fast if not faster than the 180, and if you ignore the cyano, it’s absolutely algae free. Even the glass stays spotless, unlike the hard water 180.
 

CJayT

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Little late, but I've ran 2 successful nano tanks this way, no filter, ferts and with and without Co2. Light was just shy of medium too. Surface agitation seems to help alot though. The tank is pretty well stocked with fish though and they're fed regularly, so the water gets some nutrients from the fish food.

Second pic is pretty newly planted. Not grown out much yet
...
 

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