I've found that the drier the soil the better, the gnats love wet soil to lay their eggs. I've also heard of putting a layer of sand over the potting soil to discourage the qnats from laying eggs. I used to water with a hydrogen peroxide mixture. About 3 years ago, I finally got tired of gnats flying all over the house, so I confined my bulbs, and other plants (brought in the house for the winter), to a heated glassed in "sunroom", which is closed off from the rest of the house. I put up fly paper strips on the glass windows: not very pretty, but effective for the 3-4 months that I use the room for plants. The gnats fly toward the outside light and get stuck. This keeps the gnats down to a reasonable level. When the flowers open, I bring the cut Amaryllis into the house to enjoy as cut flowers. I put a pinch of sugar into the vase, and I think they last just as long that way. Of course I am not looking for seed or trying to hybridize them.
