Mini Stainless Steel Hygrometer – Terrarium Humidity Meter

KEEP AN EYE ON YOUR LITTLE MOSS WORLD 🌿

This miniature stainless steel hygrometer provides a simple way to monitor relative humidity inside terrariums, mossariums and other enclosed plant displays.

At just 28mm across, it can sit discreetly amongst the moss without taking over the landscape. It’s particularly useful inside closed terrariums, where humidity can build up and conditions are harder to judge from the outside.

SMALL AND SIMPLE

• Miniature 28mm diameter
• Stainless steel casing and finish
• Measures relative humidity
• Clear analogue dial
• No batteries required
• Compact enough for small terrariums and mossariums
• One hygrometer supplied

WHY MONITOR TERRARIUM HUMIDITY?

Moss enjoys a humid environment, but constantly saturated conditions can encourage mould and other problems.

A small hygrometer gives you a quick indication of the moisture level in the air and helps you notice changes inside your terrarium. You can use the reading alongside visible clues—such as condensation, dry moss or saturated soil—to decide whether the container needs misting or ventilation. (Here's how humidity cycles inside a closed terrarium.)

HOW TO USE IT

Place the hygrometer inside your terrarium with the dial clearly visible. It can rest on the surface or be positioned amongst plants and decorations, but should not be buried in wet soil.

After opening, misting or moving the terrarium, allow the hygrometer time to adjust before judging the reading. Avoid spraying water directly onto the dial or submerging the instrument.

READ THE WHOLE TERRARIUM

Humidity readings are most useful when considered alongside the condition of the moss, soil and glass.

• If the moss looks dry: add a light mist with a fine plant mister and monitor the conditions.
• If the glass remains heavily fogged: remove the lid temporarily to release excess moisture.
• If water is pooling in the base: stop adding water and allow the terrarium to ventilate.
• If conditions appear balanced: leave the miniature ecosystem to get on with things.

There is no single perfect humidity reading for every terrarium because the ideal conditions depend on the moss, plants, container and ventilation. Not sure what a "good" reading actually looks like? Our guide to reading your terrarium hygrometer sets out sensible ranges for open and closed terrariums, and what to do if yours is reading outside them.

PLEASE NOTE

This miniature analogue hygrometer is intended as a helpful guide to conditions inside a terrarium. It is not laboratory-calibrated equipment, and small differences between individual readings are normal.

Use it to monitor general humidity and changes over time rather than relying on one exact number.

CARE

Keep the hygrometer above standing water and avoid spraying it directly. If moisture settles on the casing, wipe it gently with a soft, dry cloth.

For more guidance on balancing moisture, light and ventilation, read our live terrarium moss care guide or our hygrometer reading guide.

FREQUENTLY ASKED QUESTIONS

What does the hygrometer measure?

It measures relative humidity—the amount of moisture present in the air inside your terrarium.

How large is it?

The hygrometer measures approximately 28mm across, making it suitable for small terrariums and mossariums.

Does it need batteries?

No. It has an analogue dial and requires no batteries or charging.

Where should I place it?

Position it inside the terrarium where the dial remains visible. Avoid burying it in soil, placing it in standing water or spraying it directly.

Is it completely waterproof?

No. It is designed to measure humidity in the air but should not be submerged or soaked with water.

Is the reading exact?

It provides an approximate indication of humidity rather than a laboratory-calibrated measurement. It is most useful for observing general conditions and changes over time.

What humidity should my terrarium have?

There is no universal target for every terrarium. As a starting point, closed terrariums generally do well around 80–95% relative humidity and open terrariums around 50–70%—see our hygrometer reading guide for the full breakdown. Use the reading alongside the appearance of your moss, plants, soil and condensation to judge whether the environment needs moisture or ventilation.

Carefully packed in Bristol by The Moss Fairy. Free UK delivery. International delivery calculated at checkout.