Love planted tanks! Go with dirt! trust me! buy a bag of miracle gro organic potting soil and a bag of miracle gro organic top soil, mix them 50/50, add 2 cups of natural clay kitty litter, or take clay (the kind you use for making pottery) and a cheese grater, and grate the clay into small crumbly pieces. mix it all up, and vioala! put 2" of this on the bottom of your tank, then cover that with 1-1.5" of the sand of your choice over that, then plant the plants into the sand, and they will root into the soil and feed themselves, and the sand keeps the soil out of the water. if you like gravel, put it over the sand. sand is available at home depot. I use this method, and I don't dose anything. I then built a diy algae scrubber for filtration to keep the algae away. I also use diy co2, (sugar, water, yeast, 2liter bottle) plants grow best in soil, not gravel.