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Jnad 01-26-2013 09:07 PM

Dirt tank cloudy
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I am going to start a big npt dirt tank. Just to test out the dirt/soil i am going to use i have started a small cube 30x30cm. This test tank have been running for two weeks but i still Get some cloudy water after a week with no water change.

Is this normal for dirt tanks? How long does your dirt tanks take to clear up?

I have used 1 inch of soil and 1 inch of 2-4mm gravel for cap.

Hoping for some inputs


Rich Guano 01-27-2013 06:18 AM

What up Jnad!

Lay out the steps you took when you built up the layers of dirt and gravel and water. Describe the "dirt" you used. This is very important as you may be dealing with suspended clay. The best way to test the dirt for clay is to shake the dirt up in a jar full of water and observe how it settles.

Are you running a filter? Describe the filter.

Jnad 01-27-2013 10:51 AM

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Here is the steps as good as i can in English :)

Soil: this soil have no added ferelizer, somewhat black in color, not brown.
I took the soil directly from the bag, just taking out the chunks and Wood bits that i could find. I put 1 inch of soil in the tank and soaked it in water. Then i planted the big rooted plants (svords) directly in the soil. Then i cap the soil with 1 inch of 2-4mm gravel and planted the rest of the plants. Filled the tank up and did a couple of water changes to get rid of the black water. After that i have done two waterchanges every week for two weeks. The water Get a small brown look after about 4-5 days.

The filter is a Aquael sponge filter, i have now stopped the filter and done a waterchange. The water is now clear and i wil try to let the tank stand for some days with no filter and no circulation.

I did find some traces of soil on the leaves on the sword plants, could it be air or gasses from the soil that explode into the water column bringing soil particels into the water?


BruceF 01-27-2013 01:16 PM

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I think it is pretty normal. You might want to soak the soil before you put it in th tank. Change the water a few times. You might want to use a less porous cap like sand.

Rich Guano 01-27-2013 01:51 PM

Very Good Description, It translated very well into English. Not the Queens English mind you, but into the melting pot English we Americans call.. um... English. ;)

OK, I see how I can help.

First off the soil seems to be ideal. The rich blackness indicates it is composed of organic materials and probably contains very little clay if any at all. Clay actually is a good thing and is often added to the soils, but we do want to avoild colloidal clay as it will stay suspended in the water column.

Second you stirred up a bunch of murky water by over-soaking the soil before adding the cap. You see, you added water to the soil and basically stirred it around (like making chocolate milk) when you added the swords. Then the dirt suspended in water rose though the gravel once all the water was added.

There are two competing methods to solve this. One is to add the top cap of gravel while the soil is still dry. You should use a deeper top cap of 1 1/2 + inches in the case of gravel.

The second is to wet the soil before adding top cap, but do not add too much water. The goal is to have the soil feel like a rung out sponge (soft, not dried out). You just want to re-hydrate the soil, not turn it into mud or muddy water. And give the soil plenty of time to soak up the water before you start to stir it or cap it.

Lastly you will have to do water changes if the water is discolored, and run a power filter (Hang on Back, whetever). Your water should be clear after just a couple changes and several hours of filtration.

Since this was a "test" tank are you willing to dump it and try to rehearse this again before moving onto the big tank?

I would like to hear the results of the next test.

I hope this made sense.

Rich Guano 01-27-2013 01:57 PM


Originally Posted by BruceF (Post 2365874)
I think it is pretty normal. You might want to soak the soil before you put it in th tank. Change the water a few times. You might want to use a less porous cap like sand.

Hey Bruce,

I like sand too. I am working on which is better sand or gravel. I like the capping properties of sand, I like the look of sand. But from what I know about gravel, it is allows the nutrients from unconsumed organics to fall back through into the soil, thus completing the cycle, and allowing the soil to remain rich for many years. I believe I can achieve the same result with sand by using snails and worms, but I have not completed my studies yet. I will open a new post on this subject.

BruceF 01-27-2013 02:25 PM

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I’ve used sand long enough to know that it gets plenty ‘dirty’. I sometimes add a little pea gravel to the potting soil and then cap that with sand. Other than I what I do I don’t know.

Jnad 01-27-2013 02:32 PM

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Tanks for your replies.

Yes i will redo and test this soil once more in this small tank if the cloudyness dont go away.

My local hardware store do have sand that i possible could use for capping the soil. It has a grain size of 0,2-1,0 mm.

What do you think, is this a better option than the 2-4mm gravel i am using now?


Rich Guano 01-27-2013 02:44 PM

That's what we are trying to decide just now. I just opened a poll in the low tech forum. (sand vs gravel)

That sand is a great idea. I have used Pool Filter Sand successfully for years. 0.4 to 0.6 mm grain size. But I have not yet used it over dirt. My only concern is that the grain size is large enough to allow nutrients to fall back into the soil, thus extended its useful life.

tiggity 01-27-2013 03:52 PM

You'll be fine, it will be cloudy for a few days but after wc's and your filter running it will settle and clear up

Jnad 01-29-2013 07:08 AM

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Did a water change on saturday, the water seem to stay clearer now, but i have no circulation or filter in the tank, i stopped it on saturday, this could be the reason that it looks clearer now.

But i do still see dirt particels on the plant leaves, could the problem be air or gasses that burst inn to the water column taking dirt with it?

I will wait a couple of weeks more, if it not clears up i will try too cap the dirt with the sand with grain size 0,2-1,0mm.

If that also fails i might consider just trying cat litter (burned clay with no additives) as the only substrate, flourite is to expensive for me.

I was hoping to have some succsess with dirt tank though:(


Jnad 01-29-2013 08:41 AM

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About the use of sand as cap for the soil, i reading in Walstad's book that the soil may beacome very anaerobic if the grain size is too small?

Any experiences?


Rich Guano 01-29-2013 10:00 AM

Who had the right to give anaerobic soil a bad name? Is it really a bad thing? What about the use of trumpet snails and blackworms?

Jnad 01-31-2013 09:02 AM

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My patience run out:) changing the gravel to sand just now :)

If that dosent work i will try cat litter as only substrate.

If that dosent work either i will go back to saltwater tank :)

Jnad 01-31-2013 07:20 PM

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The cube have been running for 7 hours now with sand cap, everything looking good so far. Crossing fingers:)

When looking at the dirt and the sand cap layers i actually see dirt/muddy water rising up trough the sand cap. It have not reatched the top of the sand cap yet. I hope it not will.


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