That is really awesome!
I've considered trying this, but I was sure they would croak. Instead I've opted to just keep growing them in the fish tank. I'm not entirely sure my plants are tropical and not temperate aldrovanda...they've been going strong for years now in any case!...but maybe they would do better with a dormancy if in fact they are temperate?
How long where they kept in the fridge? Did you change the water at all or do anything else special?
Do they stay on your grow rack all during their growing season?