Introduction: Pico Aquarium in a Mason Jar (almost Maintenance-free)

About: I like to make / fix / improve "things"...


today I noticed the "mason jar contest" and thought it would be the right time to finally publish an Instructable for my "pico aquariums". I´ve been experimenting on those for some time now (years to be exact) and always thought to myself; "Damn, this works so well and is so simple, you have to make an `ible for this, parents and kids will love it...".

So here it is,

The guide to an (almost) maintenance free Pico-Aquarium in a mason jar with living plants and snails

  • Cheap
  • Easy to set up
  • Decorative
  • Closed, almost self-sustaining micro-ecosystem
  • Not hermetically sealed, you can still intervene at any time
  • Plants and snails can survive weeks, even month without any intervention
  • Suitable for kids in preschool age
  • Portable

Step 1: How It Works (simple Version)

This setup represents a really small closed and self-sustaining eco-system. All it needs from outside the jar is a little energy input (light) to keep it up and running (or better: metabolizing).

The plants (and algae) in the jar produce oxygen via photosynthesis if exposed to light. The snails breathe in this oxygen and breathe out carbon dioxide and nitrogen, which the plants need. The snails also eat tiniest and almost invisible algae growing on the plants and on the inside of the jar and keep it it clean. Their leftovers (snail poop) are then metabolized by micro-organisms, whose leftovers are the nutrients which the plants and algae need to survive and grow.

Sounds simple, but in reality it´s a little more complex:

But as opposed to classic "open" aquariums, all the gases and microbial metabolic products stay inside the closed containment and are reused/recycled/re-metabolized. The food for the snails is not regularly added from outside, but grows in the containment, maybe you might need to feed a tiny amount once in a while to keep them growing.


Important: It seems like a few people only read the topic and are concerned about the well-being of the snails in a closed containment.

  • This is not an hermetically sealed environment like the so-called "ecospheres" or alike.
  • You can always open it, feed the snails and/or change water if necessary.
  • Don´t put the jar in a place with direct sunlight! A bright place is fine, but direct sun might kill the snails, they will get literally boiled while your away and you won´t notice.
  • You have to take care of it, but a lot less frequently as compared to classic aquariums, plants or other pets.
  • The recommended plants and snails are very undemanding and able to 'survive' weeks or month without intervention, once a balance is established. They can live, settle and breed in much harsher environments.
    But if you care for them, they will surely do a lot better!
  • The closed lid is intended to prevent evaporation of the water in such a small containment. If you prefer to leave it open, you will have to change water regularly (e.g. almost daily), not only fill up evaporated water, or things might get out of control.
  • I recommend to keep the lid closed most of the time and only open it to feed tiny(!) amounts, or change water if necessary. (In the start-up phase and until you observe recognizable algae growth, or if regarded as necessary afterwards).
  • If you still fear to suffocate the snails, you might consider to punch a hole into the lid, but still keep it closed. Unnecessary, as long as you keep living plants in the containment which regularly get some light, the snails will do fine. Not recommended, but optional.

Step 2: Materials and Tools

What you need:

Hint: If you got a friend or colleague with an aquarium / fishtank, tell him/her about your project and ask him/her if he/she can provide you some samples/supplies. Easiest and safest way and most of the aquarists will be more than happy to give away some excess "material" and good advices for free.

  • Mason jar(s) with an airtight lid (0.25 to 0.5 litres worked fine for me, less can get a little complicated, the bigger the more uncomplicated to maintain)
  • Soil:
    I used natural black sand (not artificially coloured) from an aquarium store (see picture). Not the cheapest solution, but all natural and not spray painted like the cheap alternatives. You should wonder if it says "Do not rinse in hot water" on the label.
    You can use "normal" sand or gravel as well, just make sure you rinse it thoroughly several times until the water water you drain after rinsing is really clear.
  • Small aquatic plant(s):
    Tiny cuttings/offshoots of "anubia barteri var. nana" worked best for me. These plants are very sturdy, slow growing and if kept in a small containment without an excess of nutrients, they keep forming many small leaves instead of fewer big leaves, which is undesireable in this special case. Some strains of "java moss" (vesicularia dubyana) works fine as background accent. But these are only recommendations, feel free to experiment on your own with different plants, but I recommend using slow growing species
  • Snails:
    Your pico-aquarium can work without them for a while (plants only), but if placed in daylight you will notice it will clog up with algae at some point. Suitable for living in such a small space are ramshorn snails (Planorbarius corneus) and/or bladder snails (Physella acuta). Add max. 2 ramshorn snails per 0.25 litres of your containment, or 3-4 bladder snails.

  • Stones (optional):
    For decoration and scaping a miniature landscape in your jar. I used small pieces of slate which corresponds to the colour of the soil I used. You can use other stones as well, but I recommend slate, lava rocks or flint, which almost don´t react to the surrounding water, don´t use limestone or sandstone.

  • Last but not least, water:
    Seems quite obvious and simple, BUT;
    I recommend using water taken from an aquarium with healthy plants and fish in it, which was set up at least several month, if not years ago. Ask a friend maybe.
    This water contains all the micro-fauna (bacteria) and micro-flora (algae) which is needed to get the metabolization and food growth processes in your (tiny) containment started.
    Tap-water might or might not work. Make sure it´s free of chlorine and copper (most older boilers use copper pipes, so if you use preheated water from your tap it might be deadly for the snails), open tap and let the COLD water run a while, after that fill a containment with water and let it sit for a while until it is about at room temperature before you use it).


  • a little spoon to fill in the soil
  • long tweezers and/or chopsticks come in handy to arrange plants and decoration (not shown)

Step 3: Add Soil

Step 4: Add a Little Water to Let the Soil Settle

Add some water and sway the jar a little until the soil is spread out evenly.

Step 5: Add the Plants

If the soil is soaked and evenly spread out, add the plants. Optionally use stones to keep them in place.

If you use Anubias be sure to not bury the rhizome (the "stem") in the soil, as it will rot. Place the rhizome above the soil and the roots will grow into the soil.

Step 6: Carefully Add Some More Water

Step 7: Time to Introduce the Inhabitants to Their New Home

Put the snails in. Check back for Step 2 for the recommended number of animals regarding the volume of your containment.
Don´t add more than recommended, as the snails will starve. Don´t add less, as your "aquarium" will get clogged up with algae in short time.

Step 8: Almost Done

Fill up the jar with water to max. 1 cm below the rim. Put on the lid.

Don´t worry about bubbles or dull water, it needs some time to settle and will clear up by itself.

Note: Do NOT fill the jar up to the rim with water and leave some space for air! The snails I recommended have lungs, not gills. They can breathe submerged though, but they need to fill up their bladder with air to be able to gain oxygen from the water. Otherwise they will drown (sort of).

Step 9: Done


welcome to the world of aquarists ;)

A few notes for you:

  • "Almost" maintenance-free doesn´t mean you don´t have to care. These containers and its dwellers can survive weeks to month without interference, but having a look at them once in a while won´t hurt either you or the inhabitants. Check regularly if plants and snails are doing good, open the lid and have a smell. If it stinks, something is going wrong and you need to change water and/or rebalance the plant/animal ratio.
  • Don´t put the jar in a place with direct sunlight! A bright place is fine, but direct sun might kill the snails, they will get literally boiled while your away and you won´t notice. The snails I recommended feel comfortable in an environment of about 5 to 25 °C. So they don´t need an additional heater, but they also don´t like to get boiled.
  • Don´t fill the jar up to the rim with water and leave some space for air! The snails I recommended
    have lungs, not gills. They can breathe submerged though, but they need to fill up their bladder with air to be able to gain oxygen from the water. Otherwise they will drown (sort of).

  • Normally the snails don´t need extra food. They do fine eating what grows inside the jar, which also keeps it clean. If you experience them to chew on healthy plant leaves and don´t see any algae in the containment, you might consider feeding them.
    But carefully and in really tiny amounts (few flakes of fish food once per week or so). Otherwhise you provide algae and bacteria growth and probably end up with a little jar of stinking green mess.

If you experience any other problems feel free to leave a comment or PM me.

Have fun!

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