The Plant Lady. Nelson Water Gardens and Nursery

Plants
October is the last month to fertilize waterlilies. As the days shorten and the temperatures drop, your hardy water lilies will slowly stop growing. You'll see fewer and fewer leaves and flowers until finally all that is left is a pot on the bottom of the pond with 2-3 submerged leaves. As the lily prepares for winter,continue pruning the aging leaves as usual. The lily can be left in your pond all winter. Remember most of these plants will survive winter because they are protected by the unfrozen water in the pond. Bog plants that are not evergreen will die back after the first freeze, simply prune off the dead foliage and leave the pots alone until spring. Mosaic and Sensitive plants will not survive a Houston winter.

Tropical lilies are different
Unlike the hardy lilies, tropicals are still partying in the pond, blooming and growing all fall and on into winter. How long depends on when and how frequently cold fronts arrive. After 2-3 freezes most of the flowers and leaves will be gone until Spring. If the winter is mild then the lily will be back next year. If the winter is cold, there is a chance you'll lose the lily. See Overwintering Tropical Water Lilies.

How can I tell a tropical lily from a hardy lily?
By the leaves! The edges of Hardy water lilies are smooth. The edges of tropical lilies are crimped (botanically termed "crenate") as in the edge of a pie. Other differences: the flowers of hardy lilies are held close to the water surface, tropicals thrust their flowers 6-12" above the water surface. One of Rolf's favorite trick question for new staff members is to ask them: "Where are the blue hardy lilies?" If they paid attention, they'd know there is no such thing. Nor is there such a thing as a night blooming hardy water lily. Therefore if you have a blue flowers or a night blooming plant, it's a tropical water lily.

Fish
Fish care is easy in the winter. Stop feeding your fish when the pond water temperatures drop below 45°F. Basically all you need to do is observe your fish. If they act hungry, then feed them. If they are hovering on the bottom of the pond, then don't.

No need to worry about ice on the pond, unless ice remains on the pond surface for longer than a week. If that happens (and let's hope not), then gently create an open area by placing a can of hot water on the pond. Banging on the ice is very stressful to fish and, in rare instances, even fatal.

Fish will come through the winter in a healthier condition if you add submerged plants to your pond. With these plants in the water your fish can eat when they need to, not when you think they do.