Link for the curious On Enceladus? They'd thrive. Maybe on Europa as well. Looks like they need algae and bacteria for food though.Tardigrades are notable for being perhaps the most durable of known organisms: they can survive extreme conditions that would be rapidly fatal to nearly all other known life forms. They can withstand temperature ranges from 1 K (−458 °F; −272 °C) (close to absolute zero) to about 420 K (300 °F; 150 °C), pressures about six times greater than those found in the deepest ocean trenches, ionizing radiation at doses hundreds of times higher than the lethal dose for a human, and the vacuum of outer space. They can go without food or water for more than 30 years, drying out to the point where they are 3% or less water, only to rehydrate, forage, and reproduce.
Klackons are cool and all, but I tend to build a custom race using the Psilons as my race template. I find that their creativity and research bonuses gives them a technological edge that is hard to overcome, so I like to lock them out of the game.