Smallest Jarrarium

I have several jars of various sizes and compositions. I accidentally created my first in 2007 when my Daphnea began breeding in a 250 ml beaker which I had sealed with plastic wrap and a rubberband to prevent evaporation.

These days I keep them for donating water and substrate to accelerate tank cycling, often for keeping live baitfish.

Here is currently my smallest jarrarium-

1 mL sample vial
Chesapeake Bay sand
green algae filaments
several live ostracods