09-16-2019, 05:28 AM
Join Date: Apr 2006
| | Re: Safe T Sorb Clay for NPTs?
My results using STS in planted bowls gave much different (and better) results than those in the pint jar tests. In bowls, I didnít see much difference between using sand or STS as a soil cover. [I added a bit (~3/4 cup) of sand to the STS bowl to help hold plants down.] The KH, pH, and GH were about the same, plus no ammonia (see results). Plants are growing just fine in both bowls. In fact, I plan to keep them both going and add some RCS (Red Cherry Shrimp).
Iíll probably be using STS in my tanks, since itís so inexpensive and Sir Michael has had good results long-term with it. Folks trying it out for the first time might want to monitor the KH and the pH for first few weeks. In hardwater situations, the KH lowering might be advantageous, plus one can always add baking soda if KH and pH gets too low.
I have been recommending organic potting soils, but this might be too restrictive. The potting soil I used for the bowls was not organic and it is working well. It has a low NPK (0.023, 0.03, 0.06), but it contains chemical fertilizers (ammonium phosphate, ammonium nitrate, potassium nitrate, potassium sulfate, calcium phosphate). The chemicals are polymer-coated to be released slowly. I wasnít sure this was true, but it seems to be the case.
Photos show test results, setup of bowls, then bowls at 2 days and 26 days. The bowl on the right is the one with the STS/sand cover.
Factors that would explain the different results between bowls and jar results are:
- The ratio of STS to water was 1:16 in bowls, but only 1:3 in jars. [Jars contained Ĺ cup of STS and 1.5 cups water compared to 1 cup STS in the 1 gal (16 cups) bowl.]
- In jars, the STS depth was 1.5 inches (too deep!); in bowls about 0.5 inches. The jarís thicker STS layer would make the soil more anaerobic. Also, in bowls, the substrate had a greater surface area, and thus, increased exposure to oxygenated water.
- In jars, I started with a much more fertile potting soil (NPK= 1.1%, 0.3%, and 0.35%). Moreover, I added a dilute liquid fertilizer (1/2 cup containing 15 ppm ammonia) to the potting soil (1/2 cup) in each jar. In contrast for the bowls, I used a different potting soil (2 cups/bowl) that had a much lower NPK (0.023%, 0.03%, 0.06%), and I did not add any fertilizer to it.
- The presence of plants would oxygenate the water and root area.