Extra Storage Tanks: Tiny Storage Tanks
All credit goes to the authors of the original mod, Extra Storage Tank: Minibuffer, which are Aurora & Moonlight publishing under the username of Anicha. Since they seem to not have been active for a long time, I have taken it upon myself to port their mod to Factorio 2.0, while improving some aspects of it. And since they applied a generous license to it (MIT), I figure its okay for me to do this. I also intend to maintain the mod for a good while.
Features: The mod adds two small storage tanks, both an inline (original) and a 4-way (derived) version. They have a 1x1 footprint, a default capacity of 2,700 units (configurable), and may directly replace pipes. They are quite useful for small buffer needs and for making compact circuit networks. I greatly reduced tech research cost (it's just a smaller tank!), changed the recipe a bit and also reduced ingredient cost to more accurately reflect the storage tank's dimensions.
Graphics & Sounds: A custom "death" animation that better fit the storage tanks was created, and sound effects were added/changed as well.
Check out the related mod, Extra Storage Tanks: Steel Storage Tank, as well!