I was thinking about dirting my new tank, but I am scared of the tannins. I have had a really bad driftwood experience in the past, and really don't want to have to look at a brown tank again. I was thinking of using the Miracle grow organic stuff everybody uses, but I heard the tannins are bad. About how long and bad would it be in a 45 gallon tank?
I resolved the driftwood "tannins" problem, by collecting pieces locally. If you can, the next nice day, check out the local river or lake area for driftwood. These pieces don't contain tannins and are easy to clean. My tanks are full of nice pieces, I've been able to find close to home. If not, plan a short trip and see what's available. Take care to research and obey any restrictions to this kind of activity.
I've used Miracle Grow in the past and IMO, it's more trouble than it's worth. The biggest problem I've had with it, is if you disturb it, you'll have material floating in the tank. The stuff does nourish the plants for several months, but the nutrients don't last indefinitely and I've noticed after several months, it starts to cloud the water a little.
I've used the potting mixture in my 45 G tall and if you do large, frequent water changes, it's not bad. I've used it in pots topped with pea gravel and the plants grow pretty well with it. It has some pro and cons like most of the other soils and substrates.