Looking for the right dirt


Junior Poster
Dec 16, 2012
hey all- I know everyone loves the Miracle Grow Organic Quality Potting Mix for their dirted tanks- but I can't find any where I live.

Before I pay to ship some, I thought I would compare some other organic brands that are available.

The green label is a new organic brand from Miracle Grow- seems much more aggressive on the nutrients than MGOQPM.

The other is "Black Gold", which I think is intended for Hydroponic growing.

What is the ideal for Potassium and Nitrate I should be looking for? .05 - .10?




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Lifetime Member
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Sep 16, 2015
Hillsboro, OR
I think either is good. Higher nutrients help. Some of it will leach out initially so you need to monitor


Oct 12, 2017
New York, NY
If you're worried about your soil being too nutrient-rich, you can dilute it with sand. I always mix my soil layer with a bit of sand anyway, in the (completely unproven) belief that it helps mitigate cap breach.

Tim Harrison

Lifetime Member
Lifetime Member
Jul 7, 2017
If I had to choose I'd go for the green label if it contains peat. If you're concerned about the nutrient content you could also cut it with some extra peat. I usually go for a 1:1 mix of potting compost and moss peat anyway. I prefer soil substrate with a very high organic content.

I think soils higher in peat content have a more open structure, which is perhaps a little more conducive to root development, water movement, nutrient transference, and gas exchange. Soils higher in clay content, for instance, can become very sludgy and compact once they're mineralised. Ultimately, I guess all that really depends on what you intend to cap it with. A greater amount of organic matter might also result in higher CO2 production over a longer period.

Aquatic compost typically used in ponds is also a good option, again I usually mix it with peat. These types of products typically have nutrient levels just high enough to aid good plant growth but low enough to prevent excessive release of nitrogenous compounds such as ammonium.

Water chemistry isn't my strong point but I'd be a bit concerned about the soluble salts in the composts you've posted about, they could raise the TDS and pH. Also with both having a manure content I should imagine there will be a fair amount of ammonia leaching.
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