# Natural filters for a Walstad aquarium



## JKUK (Feb 16, 2007)

Hi everyone, I've been running Walstad style aquariums for a few years now, and have become fascinated with creating as natural an environment as possible. I have long kept earth bottomed ponds in the garden, and it seemed obvious that the two were basically the same. None of my ponds have any filtration or circulation what's so ever yet they are absolutely teeming with life. One critter in particular caught my eye, Orb shells (Sphaerium) The leaf litter in my ponds was full of them. Anyway to cut a long story short, I collected a few and popped them into a small Walstad style aquarium which was about as simple as they come. Just a tank with a light over it, no pump, filter etc. I'm pleased to report that now six years later the tank is still going strong, and to my amazement the Orb shells are not only surviving, but have multiplied to the extent that there must be at least one per square inch. The whole substrate is littered with them of all sizes. It's probably worth noting that this aquarium has never been syphoned, it is truly natural. Crystal clear too


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## dwalstad (Apr 14, 2006)

Interesting. I didn't know what an orb was until 5 minutes ago! Do you have plants in this tank?

Attached is a picture of one species of _Sphaerium_ I found on the Internet. Clams are natural filters, so I don't doubt that your tank has clear water.

Thanks for writing. You've shown us another way to enjoy natural tanks.


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## JKUK (Feb 16, 2007)

Hi Diana, 

Yes the tank is fully of plants, mainly Cryptocoryne affinis, Nymphaea minuta (self seeds everywhere), Ceratophyllum, lots of floaters including Salvinia, duck weed, Spirodela polyrhiza and Pistia stratiotes. These floaters have to be cropped every couple of weeks to keep some of the surface clear. Livestock is quite simple, just lots of guppies doing what guppies do best, a couple of Corydoras paleatus , wild cherry shrimps, small ramshorn snails, lake limpets (Acroloxus, another of my pond collections) and of course the orb shells filtering away Everything in this tank has been there from the beginning, and thus self sustaining. The thing I find most interesting is that all this is going on in a tank that only hold 20 litres of water!.....another interesting fact about this tank is its amazing stability, it has never had a water change just top up water in all this time. All parameters stay the same, nitrate is absolutely zero despite the top up water having a N03 reading of 30 ppm, and even the TDS stays the same.........

James


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## Yo-han (Oct 15, 2010)

A couple of paleatus and all these fish in 20L? I hope you mean 20G (gallon)...


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## Tattooedfool83 (Jul 7, 2013)

I'd love to see some pictures


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## JKUK (Feb 16, 2007)

Yo-han said:


> A couple of paleatus and all these fish in 20L? I hope you mean 20G (gallon)...


I'm well aware it's overstocked for such a tiny volume, not something I would normally do, and definitely wouldn't recommend. I keep it running simply as an experiment to study the principles involved.


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## JKUK (Feb 16, 2007)

Tattooedfool83 said:


> I'd love to see some pictures


http://www.aquaticplantcentral.com/forumapc/aquarium-pictures/displayimage.php?imageid=6984&original=1

This is an old pic taken from above, I'll see if I can take a couple from the side for you.


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## Tattooedfool83 (Jul 7, 2013)

Ok


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## dwalstad (Apr 14, 2006)

JKUK said:


> I'm well aware it's overstocked for such a tiny volume, not something I would normally do, and definitely wouldn't recommend. I keep it running simply as an experiment to study the principles involved.


Oh, how people underestimate the power of plants to purify the water. I looked at your picture. With this robust floating plant growth (the 'aerial advantage') and your removing plant growth every couple of weeks, you have "plant power on steroids".

This tank reminds me of the "grow-out" tank I had for my Tanganyikan cichlids. It was unbelievably overstocked with juveniles, but it worked like a dream.

That's interesting about the tank removing the 30 ppm nitrates from your top-off water. Plants also remove salt (sodium, etc) that they don't need. Because you are promoting continuous plant growth, your tank water may be better than your tapwater.

We need more experiments like this!


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## JKUK (Feb 16, 2007)

dwalstad said:


> We need more experiments like this!


Thanks Diana,

It still amazes me what can be done with such simple methods.

I'm planning to scale this aquarium up to a 240 litre with nothing more than lighting, a circulation pump and lots of Orb shells. No filtration and of course loads of floaters.

James


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## s2b (Jun 24, 2013)

James - I'm about to start a 25 liter long walstad with fish and plants similar to what you describe. I've been undecided about filtration and prefer it to be as low tech and natural as possible. You can't get more natural than a clam, so I think I'll try "installing" a natural clam filter for this tank. Would you add the orb shells when first setting up the tank, or wait until the plants have established strong root systems?

Val


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## JKUK (Feb 16, 2007)

Hi Val,

I think it will take a number of months before enough food is available for Orb shells. I like using these because they are too small to pollute the tank if you get an initial die off. Be aware that the clams you sometimes see for sale in pet shops are much larger and will not get enough food. You can easily find Orb shell in the roots of aquatic plants or just deep in the leaf litter of established ponds.

Good luck
James


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## s2b (Jun 24, 2013)

Thanks so much! It's going to be hard to wait. I once picked up a handful of wet sand on an Atlantic beach and found a bunch of tiny, purple and white clams. I didn't know a freshwater version existed. So glad you posted this!!!

VAL


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