G'day Elaine, good onya for finding 7 plump water chestnut corms for planting, especially as they came from an Asian market.Why I say this is that there is a particular selection named Hon Matai, an improved cultivar, and I would guess that the Asian folk know what they are doing, so that is the first hurdle overcome.In the traditional way, commercial way, they are grown in paddies which are flooded and drained several times, drying out in autumn and harvested in winter.They are refrigerated for human consumption for up to 6 months and this does affect the time it takes for any of those so treated to sprout. So plant them straight away in a warm spot in very moist soil, or soil with water cover no deeper than 3 inches.Once they have sprouted and are about 6 inches tall, transplant them into your chosen spot in the pond.They really should have a minimum 3 inches of depth of water in the pond and the soil depth about 6 inches or more.Ideally they should be planted in early spring and have at least 200 days of frost free growth, perfect for Florida.I very much doubt small goldfish, like comets, would do any damage, perhaps large Koi might, but I have no experience about that.Water chestnuts form an extensive root system, with plants growing up to 5 feet if planted in deep water.They will improve your ponds' eco-system by oxygenating and purifying the water and providing safe habitat for the fish and frogs.
Raccoons are quite rare in Australia, so no idea about their feeding habits.
I think you will find it fairly difficult to kill your water chestnuts in your climate and they will reward you with a decent harvest.In perfect cultivation, one corm can produce up to 3 kilos (so I have been told).
This is just my understanding Elaine, I've only been growing them for a few years, so I hope there is something of use in what I have written.
