# Crazy idea - Wabi Kusa ball as a sponge filter?



## monkeysea (Aug 19, 2007)

I just had a crazy idea and wonder if it would work. Can you turn a Wabi Kusa ball into a sponge filter?

I'm considering the design of my nano Wabi Kusa tank. I'd like a clean look with no equipment inside - that means no sponge filter, no HOB filter, no overflows, etc. But if I want to keep fish, then I need a filter of some kind.

Now, the easiest/smallest filters are sponge filters: air bubbles rising through an uplift tube create a vacuum that sucks water into the sponge where detritus gets trapped.

My crazy idea: what if you put an airlift tube INSIDE a Wabi Kusa ball? This would force water through the ball - but would it filter it? Can the Wabi Kusa substrate (soil, mud) serve as a filter medium where beneficial bacteria will grow?

I know some nano-reef folks do something very similar with live rock: drill a hole and put in an airlift tube so water gets sucked into and through the live rock for filtration. Can this work for Wabi Kusa? If not, why not?

This would make an interesting minimalist design...


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## dufus (Nov 13, 2006)

Hmm, with the airline, it would be ugly, IMO.
But, furthermore, it may break the ball apart.

Air going through water makes the water move.
that's how it all works, so i geuss it could be used like that.


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## ruki (May 28, 2007)

You can raise fish and shrimp in a small Wabi-kusa without an external filter. Just have enough plants to take care of the excess nitrogen and watch the carbonate hardness, since some plants will use that as a carbon source.

Are you talking about Marimo Moss Balls? These grow on the outside, so it doesn't seem practical to feed them from the inside.


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## monkeysea (Aug 19, 2007)

Thanks for the replies and the mention of "Marimo Moss Balls". I had never heard of Marimo moss balls before and they look pretty interesting.

However, I was originally not talking about Marimo, but instead I was talking about a DIY Wabi-Kusa with mud from a local river bank and moss/small-leafed-plants tied on the outside and/or planted in the mud ball.

After making my first Wabi-Kusa, I realized that, at least with the mud I'm using, the ball is a little fragile - moving it even a tiny bit in the water unleashes a "mud storm". So, I would be a little wary about running an airlift tube through the ball.

Furthermore, I guess that mud that is sticky enough to stay in a ball shape is not porous enough to let water flow through like a sponge filter. I guess that if I tried to make the Wabi Kusa ball into a sponge filter, the uplift tube - which should be gurgling sponge-filtered clean water out of the top - would instead be sputtering muddy water out of the top and slowly disintegrating the ball. In other words, a sponge filter works because the filter material does NOT get sucked into the uplift tube, but instead serves as a static barrier between dirty water and clean water. Mud, by itself, can't serve as a static water barrier and would get sucked into the uplift tube.

However, moss might be able to serve as a filter medium... hmmm....

I guess the basic idea, that I still think has merit, is that a sponge filter causes water flow through an airlift tube and thus traps detritus from the flowing water into a (non-living) sponge. This detritus is beneficial for plants. So, can't you do away with the sponge, and use plants themselves (e.g. moss, or plant roots) to trap the detritus as it flows through the airlift tube? This way you would have an all-natural mechanical and biological filter that never needs to be cleaned or replaced.

Is this possible?


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## ruki (May 28, 2007)

re: airlift filter through moss.

I think you can go a step farther and just skip an artificial filter, if you carefully monitor your water and have enough plants to consume the nitrogen released by the fish.

I've been trying this with some shrimp for the past month and they are still alive


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## Aplomado (Feb 20, 2013)

Emergent plants are better at removing wastes than submerged ones- you could try something like that.

Perhaps you could just hide the filter behind hardscape?


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## jasa73 (Jun 3, 2007)

What if instead of dirt you used an actual sponge cut into a sphere? It'd have to be large enough to accommodate the plants. Wrap it in some moss and then stick the plants in.


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