How to choose a Jar
While these micro-aquariums are usually called “jarrariums”, they do not necessarily need to be built in a jar. Any container that is transparent will work. The ideal material for the vessel is glass, as it strikes the best balance between visibility and impeding algal growth. Size is also an important factor. While this project could technically be accomplished in something the size of a drinking glass, bigger is always better. You’re striving to emulate a pond, but it’s hard to fit those on a windowsill so you gotta get as close as you can. A bigger container will allow for more life, support a wider variety of organisms, reduce the frequency with which you have to do water changes, and provide a buffer to the natural buildup of chemicals.
Qualities to look for in a Jar
You might want to take into consideration the width of the mouth. You don’t want to build a ship-in-a-bottle; that’s way too much effort. In the best case scenario you will be able to easily fit your whole hand in the vessel. It will make decorating and planting much easier, as well as any future maintenance you might need to do (like trimming plants).
Opacity is also an important factor. You want your jar to be as clear and transparent as possible. Stay away from colored glass too. With few exceptions, you want as much light to enter the jar as possible. Colored glass filters out certain wavelengths of light, and anything less than totally transparent blocks light too. Your plants will not appreciate this. Besides, you don’t want to obstruct your view of your little biome!
Don’t overlook odd vessel choices! Jarrariums can be as much about the aesthetic as they are about the experiment. The particularly artsy among us might be inspired by a large glass beverage server with a spigot, for example. What to do with the spigot, then? You could remove it and seal the hole with a plug or cork. Or you could leave it! It will make water changes that much easier!
If you fear that the integrity of your vessel is compromised, don’t worry! You can make just about anything watertight with some silicone sealing gel. Make sure to get the kind that is aquarium safe, it should be sold at both pet stores and hardware stores. Apply it liberally to a dry surface. Give it a couple days to harden, then shave off the excess if you’re concerned about the aesthetic.
Finally, you could just choose a fishbowl or aquarium. Jarrariums are defined by the goal of creating a self-sustaining ecosystem more than by the vessel they are built in. While it might incur more costs (such as acquiring an aquarium in the first place), using a ready-built aquatic container does not make it any less a jarrarium.
So you’ve got yourself the ideal jar, what’s next? Why, choosing the substrate, of course!