I am not the bravest person when it comes so socializing, so I am not very forum-savvy. However, I am a nerd who loves to learn and I am going to do my best to share what I learn just in case it helps you all. ᕦ(ò_óˇ)ᕤ
You could use Mosquito Dunks (BTI) which uses a bacteria to kill mosquito larvae, but are safe for fish, pets, and adult insects.
Just a guess here, but it could be one part being in an air-tight sealed container, and one part being stored in a cool location. The porous nature of clay might also be an advantage somehow too.