# Worm castings as soil layer?



## terazfish (Dec 30, 2020)

I have heard from my LFS that I could use worm castings as my soil layer. One benefit is not having to sift out the larger woody debris you find in organic potting soil. Has anyone had success with worm castings or should I stick with organic potting soil?


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## mistergreen (Mar 3, 2007)

I think it could work. I'd mix sand into it so it's not too rich in organics.


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## Michael (Jul 20, 2010)

Worm castings vary a lot depending on what the worms eat, but castings usually have higher fertility than we want in an aquarium substrate. Use a very thin layer or (better) mix them with an inorganic high cation exchange capacity substrate like Safe-T-Sorb or plain cat litter. I suggest no more than 50% castings, or a lot less.


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## Daz (Aug 15, 2020)

I used 2.5 cm of worm castings in my most recent tank. It took about 3 months to stop getting green algae. Now, plants are growing great and there is evidence of a nice CO2 production. I do 50% water changes every week, I dechlorinate water during a week in a 10L bucket and once a month I add a spoon of vermicompost to the dechlorination bucket as fertilizer (because I have no fish, and I don't want to overfeed my shrimp and snails). I get some thread algae growth that requires cleaning at least once a week.

This is my tank right now
https://photos.app.goo.gl/WZ8dnLEPCRWc7zn87


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## dwalstad (Apr 14, 2006)

Worm castings are a wonderful natural fertilizer packed with nutrients, but they are not recommended as a soil substitute. According to this educational article, worm castings have an NPK of 5:5:3. That is *50-100 times* more nitrogen, phosphorus, and potassium than what I use or recommend. For example, the NPK of the organic soil (MGOC) that I used for my successful shrimp bowls was 0.1:0.05:0.05. See article. Even then, some hobbyists complained about algae from excess nutrients. 

Not to worry, though. Your post shows that you can set up a tank with a very nutrient-rich substrate and eventually get a nice tank. The trick is doing enough water changes to remove all those excess nutrients.

Folks: Aquatic plants don't need an ultra-rich substrate. They are shade plants with CO2-limited growth. Excess nutrients encourages algae and water changes more than it helps plant growth.


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## Daz (Aug 15, 2020)

dwalstad said:


> Not to worry, though. Your post shows that you can set up a tank with a very nutrient-rich substrate and eventually get a nice tank. The trick is doing enough water changes to remove all those excess nutrients.


Indeed, many aquatic plants do well with low light, the tank I set up is packed with plants that grow under direct sunlight in my area (they even avoid tree shade), so I went for a high light, high nutrient aquarium.


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## terazfish (Dec 30, 2020)

Thank you all for the replies! Your input was helpful for determining how I want to setup my first dirted tank.


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