Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Part of the goal of MTS is to mix the fertilizers and minerals into the soil ahead of time so there might be less water column dosing later. So add whatever you need to in the beginning. Make whatever sort of mix is right, depending on the soil you have. Some soils already have some nutrients.
You might run a test with a handful of your soil.
Put it in a jar of water (the same water you will be filling the tank with- tap, RO, a blend...) and shake it really well. When the water settles test the GH, KH and pH. Compare that to the tap (or whatever) before you added the soil.
Possibility A) If the soil is high in minerals the GH, KH and pH may rise over a few days.
Possibility B) If the soil is removing the KH then the KH and pH will drop over a few days.
Next question is what sort of fish do you want to keep?
If your soil is like A, and you want to keep hard water fish, then add a bit of dolomite, limestone, crushed coral or whatever to enhance the effect. The soil probably already has some of these minerals, but a bit more is probably just fine. Do not add much if any peat moss.
If your soil is like A, but you want soft water fish, add peat moss and test again. You do not want many minerals in the water for soft water fish. Try perhaps 25% peat moss + 75% soil. That is a lot of peat moss.
If your soil is like B, and you want hard water fish, then add lots of dolomite, limestone, coral sand or oyster shell grit (perhaps some of each).
If your soil is like B, and you want soft water fish then add peat moss, and just a little dolomite. The plants will need the minerals, but you do not want to use enough dolomite to affect the water very much. The softening effect of the soil may be just what you want to keep soft water fish.