Sponge Filters in Planted Tanks?

Discussion in 'General Planted Aquarium' started by Troy, Oct 9, 2016.

  1. Troy

    Troy Member

    I'm in the middle of rebuilding my fish room and would like to incorporate the Walstad method planted tank to the fish room. However I was planning on running sponge filters as my main filtration for the system. Will the surface agitation from the sponge filter degas a majority of the CO2 in the water leading to my plants not thriving? I wasn't planning on injecting any CO2 as non of the plants I have on hand require injection. Thoughts/Personal Experience?
  2. Marine590622

    Marine590622 Advisory Board Staff Member

    The Walstad method of planted tanks means the plants are the filtration. If you are running sponge filters the sponge is serving as a competitor to the plants for the available nitrogen. Often, the solution to algae problems in a problem tank is to remove the additional filtration and let the plants do the work. The first thing you need to decide is this, "Is the primary focus of the tank the fish, or the plants?" Once you have determined that you are in a better place to determine how to set up the tank.

    A direct answer to the question of the surface agitation is yes. Surface agitation is going to reduce the availabe co2.
  3. Jason K

    Jason K New Member

    Shouldn't the sponge filter mostly just convert most of the nitrogen to nitrate? I would think the amount of nitrogen truly lost to the system by denitrification would be small in the grand scheme of things. Or are you talking about the nitrogen incorporated into the bacteria that are growing themselves?

    The CO2 issue seems like it would be a bigger one to me.
  4. Aquaticus

    Aquaticus Administrator

    Most plants use ammonia more efficiently than they do nitrate or nitrate, so in the Walstad method, you don't need additional biological filtration other than the plants. A powerhead for water circulation is a nice addition. An air driven filter will have a negative impact on the natural CO2 levels, but IME, it isn't really a problem for the plants. I recommend her book. It's a fun read!
    Jason K likes this.
  5. Marine590622

    Marine590622 Advisory Board Staff Member

    What he said. We will be going over the Nitrogen cycle this Saturday, and we can discuss the difference between biological filtration and using photosynthesis as filtration. But Eric's point that if you convert the ammonia to nitriate and nitrate the nitrogen becomes mostly unusable by the plants. Adding a form of Iron back to the tank can revert the nitrate and nitrate to ammonia but why do that when you can just remove filter media and stop starving your plants.

    I remember one case I read about on the AGA site years ago where the end results to a hair algae problem was to remove the filter media from the canister filter and collect the hair algae and put that into the canister filter to break back down and feed the plants.
  6. Chuck

    Chuck Well-Known Member

    In the Walstadt method, you are trying to capture the nitrates and bring them down to the roots. The roots absorb the nitrates a lot more efficiently. The anaerobic bacteria in the soil do a lot more efficient job of converting the nitrates to a useable form.Rooted plants will only absorb nitrates out of the water column when they are starving. Essentially , you can add co2 and light all day , but if you don't get the nutrients to the plants in the right place, you are just going to feed the algae.

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