I was just wondering this very thing the other day. I just read One Straw Revolution (new to this site, so not sure if this book ever gets discussed, but it's amazing) and in that book Masanobu Fukuoka says that it is not necessary at all to grow rice in water, and in fact it is not healthy for it. Especially not in stagnant water, as is probably the case in the turtle sandbox. I was also just reading Rodale's on the subject this morning and they say that rice can be grown in the same manner as corn. So, if you can grow corn, apparently you can grow rice.
I just decided the other day to sow some rice in my little fishpond. I threw some grains in around the shallow ends. I have three goldfish in there and I see they are leaving the rice alone. I hope it will provide them with some nice cover and nutrients/O2 when the plants grow, and they will fertilize the plants in return.
I'm sure you're right, Maikeru. I'm just repeating Rodale's. But it makes more sense to say that if you live somewhere you can grow corn, then there is probably a variety of rice that will succeed there as well. They didn't specify which kinds do best where. I look forward to finding out someday!
We are growing out our seed supply this year with the research seed we got from the USDA. Over the next few years we will be selectively planting for rice that performs well in vermont.