Unpopular opinion but I think we have a civic responsibility to put them on probes and crash them into every planet in the solar system. Those cute little water bears are nature's survivors.
There's probably a better word but it resonates with some people.
The desire to preserve other planets for the remote chance that there's life there and we can study it before turning up anyway and ruining things is misguided. We are the only known life in the universe, it's incredibly irresponsible to not propagate such things (just in case)
Fish and humans have vastly different diets, and human feces contain different bacteria and viruses than fish feces. You can absolutely pollute an ocean with sewage. Please try to educate yourself.