[fjacquet]

Hello !
We are three french students and this forum seemed to be well-informed about one of the methods we'd like to use. We want to compare an aquarium with an artificial filtration and one with an all-plant filtration to see wich method is best-suited.
We thought about the Walstad method for the all-plant filtration but we're not very experimented and we could use some advice. We don't know if other better methods exist. For now, we have thought of the following plants:
-sagittaria subulata
-java moss
-duckweeds
-anubias
-elodea
-vallisnerias

Merci ! ;-)

 

[Michael]

Welcome to APC!

For plant-only filtration, you will want to plant densely right from the start, and will want more fast growing, easy stem plants in the mix. Your current list is fine, but has only one fast growing stem, the elodea. I suggest you increase species diversity in this category with some easy species from the genera Hygrophila, Bacopa, Ludwigia, or Rotala.

Duckweed and other floating plants are really helpful. You might also consider Limnobium, Salvinia, Najas, Pistia stratiotes, or Ceratophyllum.

Plants are more effective at removing waste if there is some water circulation. If it doesn't violate the experimental procedure, add a small recirculating pump to your plant-only tank.

Bonne chance, and let us know the results!

 

[Diana K]

Part of what you need to consider is if conditions will be the same in both sets with the only difference being the filter media.

Same substrate. If you are running a tank with no plants I do not think that a Walstad style substrate is good in such a system. I would use something non-reacting, such as sand or fine gravel. That way both systems (plant-filter and equipment-filter) will have fewer variables.
Same equipment (light, heater, filter). The 'plant filter' system will need the same amount of water movement as the 'equipment-filter' system. Perhaps the same filter with no media? Or just mechanical media?
Same livestock, and a careful scale to weigh out the food.

I would cycle both systems before beginning the tests. Then a big water change to make sure they start out as close to the same as possible.

What tests will you be using?
What media will you be using in the 'filtered' systems?

 

[neilshieh]

michael and diana made some excellent suggestions. While I've never actually had a tank with plant only based filtration, I do have extremely low maintenance tank with only a sponge filter running for biological filtration. Plants that come to mind that I would suggesting using: najas guadalupensis, salvinia minima, duckweed, hygrophila difformis (water sprite), rotala rotundifolia or indica. You want quick growing plants that can just suck up all the nitrogen compounds. Java moss is a good choice, but anubias less so because it's a heavy root feeder and as Diana mentioned you'd want to use either inert substrate (sand) or fired clay substrates. Walstad uses high organic substrates I believe which would really throw off readings and other metrics like turbidity.

If you want to remove any sort of organics or if they'd interfere with some sort of metric run some seachem purigen in the water circulation system for both tanks. Best of luck!