First there has been some shortages of potting soils as this is the year everyone is at home with time to garden. The good news is more potting soil will be filling stores soon so keep looking. To substitute for Osmocote potting soil look for Miracle Grow potting soil. The fungus gnats you get from indoor plants are harmless and feeding on organic matter in the soil but to keep them under control use a mulch of marbles, corks or some other barrier to keep the gnats from laying eggs on the top of your soil. Do not overwater as damp soil makes the gnat problem worse. One way to capture the critters if they do hatch is to set a white saucer  filled with water and a few drops of lemon scented dishwashing soap near the plants. The gnats fly toward the white color and lemon scent, fall into the soapy water and drown. Keep growing, Marianne Binetti