If we ever send a probe to look for life on the Jovian moons Europa, Ganymede, and Callisto, we might find tardigrades already there, or accidentally introduce them
They certainly look alien to me!
The biggest obstacle I've had with tadpoles is combating tail / finrot. It occurs when the tank water is cloudy and there isn't enough beneficial, autotrophic bacteria to outcompete the heterotrophic type. It's a delicate balance of the right amount of tank sponge filtration, and plant life. Normally, I don't eliminate the problem until the Salvinia takes over the entire tank. Most tadpoles with tail / finrot will recover as long as it doesn't ruin the entire tail.
Salvinia is very useful for allowing froglets to climb out onto.
Also-- here's a warning for those with my red expectata. Do NOT use oak leaves or almond leaves or heavy tannins. I killed my tadpoles several times that way until I decided to raise them without tannins. It makes sense since the frogs live around alkaline cliffs.