My lilies are in a net bag (like what onions come in, or the nylon/plastic bag that comes around turkeys sometimes). I use rock in the bag with the corm to weight it down. I tried different types of soil and rock and such and the
goldfish would root around in the dirt/sand/gravel/rock and make a mess. With the mesh bag, the roots can grow through and down and draw the nutrients right out of the water, and the leaves and flowers can grow through and up without being hindered by heavy rock. My sister has big river rock in the bottom of her pond that she tucked the lilies into to anchor them, but her pond is much deeper than mine, so she had the depth to put a layer of rock in the bottom.
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