Just Add Ice

[Fishkeeper]

No, no, carbon freezing is carbon, not ice. The poor things will die of dehydration. Same with dry ice, it's not water. And liquid nitrogen will over-fertilize them! Stick to plain old ice made of water, but make sure it's small cubes so there's plenty of ventilation. If you have more sensitive species, be sure you rig a computer fan in the freezer to circulate the air.