I gave up trying to keep tropical floaters all winter, they always died for me. You have to really baby them, lot and lot of light and the water must be heated with a fish tank heater to keep the water above 70 degrees.... way too much work!
The white Calla was planted in kitty litter years ago, in a large basket, and it comes back every year. I leave it dry over winter and let the tops freeze off, then take it into the green house and store dry in a cold corner of the greenhouse. It is about a foot high and waiting in a tub with just a puddle of water for now, cause it is going in the front yard pond as it is shady and does well there. I have a bulb that is growing with roots, and I wedge just the bulb in some rocks in the main pond and no soil, and it does great that way too!
Here it is last year in my middle pond..,. That one was just planted in a clay pot with small rocks.... I go lots of them everywhere.... gave some away and going to put the rest out in front pond stream this week when I finish that stream,,,,