A Tiny Sealed Under-the-Sea World: How to Make a Mini Fish Terrarium (No Real Fish, All the Charm)
Before we start, let’s clear the air (or in this case, the “water”): this isn’t about keeping actual fish in a jar.
We love fish too much to trap them in a pint-sized apartment with no oxygen or snacks.
This is about creating a sealed decorative terrarium that looks so much like an underwater scene that you’ll do a double take…every single time you pass it.
It’s like the snow globe’s breezy cousin who decided they’d rather live in a seaside apartment instead of a winter village.
And the best part?
No water changes.
No filters.
No, “Oh no, I forgot to feed you.”
This is a slow dopamine craft: a small, low-effort, high-payoff object that your eyes can rest on whenever life gets loud.
Step 1: The Jar is Everything (Choose Wisely)
Pick a jar you like looking at even when it’s empty.
I’m partial to:
Short and squat spice jars that make the “sea” feel cozy.
Tall and thin jars that feel like a deep dive.
Apothecary jars with chunky glass lids (extra dramatic).
The jar is the first moment of dopamine in this whole process…you’re already building anticipation just by choosing it.
Hold it up to the light. Tilt it.
Imagine what tiny fish would see if they lived there.
If the jar doesn’t make you smile empty, it won’t magically become exciting full.
Step 2: Build Your Ocean Floor (Pebbles, Sand, or “Vacation Souvenirs”)
Pour in a small layer of pebbles, aquarium gravel, or craft sand.
If you’re like me and have a stash of random shells from a “I’ll totally make something with these” phase, now’s their moment to shine!
Here’s the trick:
Keep it uneven. Hills and dips are more interesting than a perfectly flat bottom.
Let some of the bigger shells lean against the glass so they’re visible from the outside.
If you’re using sand, press down a few “paths” with the back of a spoon…instant depth.
This is your chance to play set designer for fish who will never complain about rent (the best kind of tenants).
Step 3: The Secret Greenery (Moss, Plants, and Mini Coral)
Fake moss works beautifully here.
The trick is to cut or tear it into tiny, imperfect tufts so it looks like something that grew there naturally.
You can get preserved moss at most craft stores.
Or cheat like I do and trim a bit of green felt into wobbly shapes.
Miniature plastic coral? Yes please. Even better if it’s painted in candy colors.
Tuck your greenery into little pockets on the “floor.” Make it uneven…one big chunk, one small sprig, one patch with nothing at all.
Our brains like variation.
Step 4: Choose Your Fish (The Main Characters)
This is where your jar stops being “pretty” and starts being alive (well, symbolically).
Go for tiny resin or plastic fish—goldfish, clownfish, even a seahorse or two.
The weirder, the better.
I once used a 2cm mermaid and no one’s ever let me live it down…in a good way.
Placement tips:
Tilt one slightly sideways, like it’s mid-turn.
Have one “hide” partially behind a shell for mystery.
Use a dab of clear glue if you want them suspended mid-water.
Every fish gets a role. Your jar is basically an underwater sitcom set now.
Step 5: Mixing the “Sea”
We’re not using just plain water here, we’re going for a dreamy, slow-moving ocean.
Pro tip: cover the bottom with resin so the sand and moss don’t shift (if you want!).
Option 1 – Layered Liquid:
Half jar water + a drop of blue or green food coloring.
Top with clear mineral oil.
Oil floats above water, catching light in a soft shimmer.
Option 2 – Glycerin Sea:
Warm water + 1 tsp glycerin + color + optional glitter.
Slows down movement so the “water” feels heavier, more tranquil.
Option 3 – Frozen Sea:
Use craft resin to freeze your scene exactly as you want it.
Holds more permanence if you are looking for consistency in your life.
Pour carefully down the side of the jar so you don’t disturb your little set.
This is one of the most satisfying moments, watching liquid fill up around your scene without wrecking it.
Step 6: A Hint of Magic Dust (Optional)
Glitter, mica powder, or even the tiniest pinch of iridescent eyeshadow can make the water sparkle like sunlight.
The key: less is more.
You want shimmer, not a glitter bomb.
Step 7: Seal and Style
Close your jar tightly.
If you want, run a thin bead of glue around the lid for extra security.
Now…decorate the outside.
Wrap the lid in twine.
Paint little wave crests along the glass bottom.
Add a seashell charm dangling from the neck.
The exterior should feel like the cover of a book…you want people curious enough to “open” the story with their eyes.
Step 8: The First Tilt
Pick it up. Slowly rotate it in your hands. Watch your fish “swim,” your glitter drift, the liquids shift. This is the dopamine drop.
It’s a small ritual you can repeat every time you need to breathe slower.
Why This Works (The Mini Science Bit)
Humans love miniatures because they give us the thrill of mastery over a world…without the stress of actually running it.
Throw in slow-moving elements and gentle sparkle, and you’ve got a visual stim toy in a jar.
Your brain says, “That’s nice, I want more of that,” and boom…dopamine!
Extra Fun Sections to Hit Our Joy Quota
Make a Whole Aquarium Shelf
Don’t stop at one. Make a family of jars:
One with a tropical reef theme.
One that’s deep-sea dark with glowing fish.
One that’s all white sand and pastel coral.
Seasonal Fish Jars
Spring: pastel water, baby fish, mini flowers.
Summer: bright blue, tropical fish, palm tree charms.
Fall: amber tint, gold glitter, leafy plants.
Winter: icy silver glitter, pale blue fish, tiny snowflakes.
Gifting These Tiny Oceans
People lose their minds when you hand them a gift like this.
Wrap it in brown paper, tie with twine, and tuck a handwritten “Care Instructions” that just says: Look at it often. Tilt when necessary. Smile always.
Display Ideas
On a sunny windowsill (the shimmer goes wild here).
Next to houseplants…green + blue = calm brain.
On your work desk for those “I can’t look at another email” moments.
The “No Fish” Version
Just shells, sand, and plants for a minimalist beach vibe.
I once made one with only white sand, one shell, and a single pearl bead…people thought it was art.
Why We Seal Them
Because part of the magic is permanence. It’s like freezing a perfect moment, you know it’s not changing, so you can keep coming back to it exactly as it is.
Closing Thoughts
A sealed fish terrarium isn’t just a craft.
It’s a tiny daily escape…a thing you made that keeps giving, quietly, without ever asking for maintenance.
It’s proof that you can create beauty with a jar, a few bits of plastic, and your imagination…and that sometimes, happiness fits in the palm of your hand.
Related Reads you Might Enjoy:
The Psychology of Tiny Things: Why We Love Miniatures, Dolls, and Dioramas
Make Plantable Seed Paper From Junk Mail: A Crafty Way to Grow Beauty from Trash
Soap Carving: The Gentle Art of Shaping Something Small and Sacred
The Cleanest Soap You’ve Never Heard Of: Soapnuts and the Science of Suds
Watercolor Painting: The Soft Art of Coming Back to Yourself
Feeling Worthless? Here’s Why the Odds of You Existing Are the Most Beautiful Miracle
