Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Have a look at my post to the thread "MTS... then winter hit".
There is a guide to using any sort of soil, though the comments make it look like garden soil, you can do the same thing to bagged mixes.
Once you have soil that has almost no floating matter (roots, leaves, sticks, compost) you can use it right away in the tank.
I would add some fertilizer tablets first, on the floor of the tank, then be careful not to disturb them. Slow release product like Osmocote is good.
Wet the soil pretty well so there is the least dust. Put the soil in the tank, rocks, driftwood... Shape the soil into hills and valleys.
Wet the soil some more, perhaps a spray/mist bottle for a smaller tank. Take this opportunity to rinse off the glass, too. Do not get the water higher than the soil.
Plant, misting often. Add a topping (gravel, sand...) after you are finished planting if you want.
Put a plastic bag or a plate over the substrate and start filling. Run the water in slowly so it seeps over the plate. This will minimize clouding.
In a larger tank you can run the water faster after it is about 8" or deeper. Aim the hose horizontally so as not to dig up the substrate.
Since this soil is an unknown as far as fertilizer and other components go, I would run the tank for a while and test for everything I have tests for.
Ammonia, nitrite, nitrate: For the plants these are fertilizers. For the fish, toxins. If ANY ammonia or nitrite show up then allow the tank to cycle to grow the necessary nitrifying bacteria to deal with these. Some soils release so much ammonia you can do a fishless cycle and not need to add any ammonia.
GH, KH, pH. If these are stable this is best. If they are changing then there is something in the soil doing this. If the soil was originally a limestone or coral parent material then the soil is likely going to make the water hard and alkaline. Think about keeping livebearers, Rift Lake fish, Rainbows...