Mossroom build journal: a 90-day observation log

This is a real build journal from a Mossroom contributor. Documented over 90 days because the most useful thing you can read isn’t “how to build a terrarium” — it’s “what actually happens after you build one.”

The build

Date: March 15 Container: IKEA 365+ jar, 1.8L Substrate: Standard closed terrarium mix Drainage: Lava rock (1.5 inches) Hardscape: One piece of spider wood, two small lava rocks Plants:

• 1 small fittonia ‘Red Anne’
• 1 small pilea glauca cutting
• 1 button fern
• Sheet moss for ground cover
• Cushion moss for accent

Cleanup crew: Added springtails on day 14

Day 1: Build day

Felt good. Plants looked healthy when I put them in. Substrate was evenly moist, not soggy. Closed the lid, set it in a north-facing window.

The fog immediately appeared. Heavy condensation within an hour.

Day 3: Foggy

Still very foggy. Can barely see in. Worried I over-watered. Posted on Reddit, got “give it time” advice. Did not open.

Day 7: Fog cleared

By day 7, the fog started clearing each morning and reforming each night. Started to look like a healthy cycle.

Plants all looked the same as day 1. No wilting. No browning.

Day 14: First concerns

The fittonia looks slightly droopy. The pilea is fine. Button fern has slight browning on the lowest frond.

Action: Opened the lid for 30 minutes. Added springtail culture. Closed lid.

Day 21: Fittonia recovery

Fittonia perked up within 24 hours of the air exchange. Realized: the air exchange probably helped more than the springtails. Started doing 30-minute air exchanges weekly instead of biweekly.

Button fern’s lowest frond fully browned. Removed it. New growth at the top looks healthy.

Day 30: First new growth

Pilea started putting out new leaves. Visible growth — they’re tiny and red when new, turning silver-green as they mature.

Fittonia fully recovered. Looking better than at build day.

Moss is greening up. Started off brownish from shipping, now solid green.

Day 45: Encountering “the wobble”

A patch of what looked like white fuzz appeared on the substrate near the spider wood.

Diagnosis: Mycelium from beneficial fungi. Normal. Did nothing.

It disappeared within a week.

Day 60: Pilea explosion

Pilea started cascading over the edge of the substrate. Already starting to look like too much. Realized I might need to trim soon.

Fittonia has visibly grown. Button fern has 3 new fronds.

Springtails: visible if I look closely. Tiny white specks moving on the substrate.

Day 75: First trim

Trimmed the pilea back significantly. Took 4-5 cuttings for propagation. Kept one in the jar, removed others.

Saved cuttings in a small propagation box — they rooted within 2 weeks.

Day 90: The state of the build

Fittonia: Thriving. Has new growth, color is vibrant.

Pilea: Recovered from trim. New growth filling in.

Button fern: Three healthy fronds, one still browning on the tip. Overall happy.

Sheet moss: Solid green, filling gaps between other plants.

Cushion moss: Grew larger, looks great.

Spider wood: No issues. Slight tannin discoloration on the substrate near it (turned slightly tea-colored). Not a problem.

Springtails: Established, visible, doing their job. No mold issues.

Water cycle: Fog forms daily, clears by afternoon. Substrate stays consistently moist. No need to add water.

Aesthetic: Lush, full, alive. Looks like a tiny forest in a jar.

What I learned

What worked

• Pre-moistening the substrate properly
• Adequate drainage layer
• Springtails from day 14
• Weekly air exchange (more often than recommended, but my climate is humid)
• Trimmed pilea aggressively before it took over
• Distilled water only

What I’d do differently

• Add fewer plants initially (was slightly crowded by month 2)
• Skip the activated charcoal (already knew but tested anyway — confirmed it didn’t help)
• Add isopods from the start for richer cleanup crew
• Use larger container (1.8L felt small by month 3)

What surprised me

• How FAST pilea grew
• How SLOW fittonia grew (in a good way)
• How resilient the system became after month 1
• How little maintenance it actually needs now

Current status (6 months in)

Still thriving. About to upgrade to a 5-gallon jar — the 1.8L feels small now.

The plants from this build have been propagated into 3 other jars and one gifted terrarium.

What this means for you

A well-built closed terrarium will:

• Settle into a stable cycle within 2-4 weeks
• Need almost no maintenance after month 1
• Show visible growth for the first 6 months
• Plateau and need trimming after 6-12 months
• Last 3-5 years before substrate needs replacing

The hardest part is the first month. After that, it’s mostly observation and enjoyment.

Want to build your own?

Start here: First closed terrarium guide.

Share your own build journal in the Discord — we’d love to feature community builds.