Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I would do water changes if the ammonia gets so high it starts burning the leaves. Some plants are very tolerant of ammonia, but some can burn with as little as 1 ppm.
So keep up the testing, and watch the plants VERY carefully.
Ammonia burns damage the cells so the plants look water soaked (Bad term for aquatic plants, but very descriptive of land plants, and it looks the same).
At the first sign of ammonia burn note the ammonia test result, then start doing water changes before it gets that high again.
If the ammonia is from the soil, it should slow down after a while. ADA soils take about 3-4 weeks to get rid of the ammonia, but I do not know if Miracle Grow Soil will be the same (one reason I want to follow this thread!)
Once the ammonia has stabilized enough that you do not have to do so many water changes, you can start to think about CO2.
Once source of CO2 in aquariums is organic matter in the substrate, decomposing, or composting- whatever term you like- microorganisms are eating these materials, and one thing they produce is CO2.
This is one of the features in a Walstad tank. If there is too much organic matter there might be problems, but I am not sure. Miracle Grow Organic Choice is mostly organic matter, and it seems to work if it is mineralized. That does not get rid of the organic matter.