Fissidens fontanus (US Fissidens): A Soft, Feather-Like Moss for Quiet Tanks

Fissidens fontanus, often called US Fissidens, has a very different feeling compared to common mosses like Java Moss.

Its fronds look like tiny green feathers or ferns, layered gently on wood and rocks. The overall impression is soft, slow, and very “forest under water”.

In this post, I’ll share how I like to think about and care for Fissidens fontanus in a simple, realistic aquarium setup.

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Quick Profile

• Name: Fissidens fontanus

• Common name: US Fissidens, Phoenix moss (sometimes)

• Type: Moss / epiphyte

• Placement: On hardscape – wood, rocks, or small decorations

• Growth rate: Slow

• Difficulty: Easy–medium

• Look: Fine, feather-like fronds with a soft, layered shape

Fissidens doesn’t grow into a wild, messy bush as fast as other mosses. It stays neater and more structured, which makes it great for calm layouts and shrimp tanks.

If you want to see how it fits with other plants I actually keep, my Aquarium Plants: Simple Guide to What I Actually Use is a good overview.

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What Makes Fissidens Fontanus Special?

A few things that make it stand out:

• Very fine texture: The fronds are delicate and small, giving a refined look.

• Structured growth: It often forms mounds or layered patches, instead of random spaghetti.

• Shrimp-friendly: Shrimp love grazing between its tiny leaves.

• Good in low-energy tanks: It doesn’t need extreme light or CO₂ to survive.

It fits well in scapes where you want a “soft green accent” rather than a dominant plant.

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Tank Size and Basic Conditions

Fissidens fontanus can work in almost any size:

• Nano tanks

• Medium tanks as detail around wood/rock

• Larger tanks as small “moss islands”

Approximate water range (it’s quite adaptable):

• Temperature: 20–26°C (can usually handle a bit warmer, but cooler side is more comfortable long-term)

• pH: Around 6.0–7.5

• GH/KH: Soft to medium-hard

If those letters feel confusing, GH, KH and TDS – the three water numbers that matter explains them in simple terms.

It usually handles typical treated tap water. As with most mosses, it dislikes sudden changes more than specific numbers.

For a broader picture of what “soft” and “hard” mean, you can also read Soft vs hard water: simple guide for aquariums.

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Light: Gentle Is Enough

You don’t need strong light for Fissidens to live.

• Low–medium light is usually best:

  • Moss stays healthy and green

  • Lower chance of algae cover on fronds

• High light

  • Can push slightly faster growth

  • But greatly increases algae risk, especially if CO₂ and nutrients are not balanced

For most home aquariums:

• Start with 6 hours of light and adjust slowly up to 7–8 hours if things stay stable

• If algae starts to coat the moss, try reducing intensity or duration a bit

Because Fissidens grows slowly, any algae that settles on it will not be “grown out” quickly like fast stems. That’s why moderate light is safer.

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CO₂: Optional but Helpful

Fissidens fontanus can be grown:

• With CO₂

  • Growth is somewhat faster

  • Fronds often look brighter and fuller

  • Recovery from damage or slight melt is quicker

• Without CO₂

  • Still very possible

  • Growth is slow, but for some people that’s an advantage (less trimming)

  • Focus on stable water and not over-lighting

If your tank is low-tech with no CO₂, Fissidens can still be a nice, gentle accent moss, especially in shaded spots.

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Attaching Fissidens to Hardscape

Like other mosses, Fissidens doesn’t have “true roots” that dig deep. It needs something to cling to.

You can attach it to:

• Driftwood

• Rock

• Stainless mesh

• Small decorative stones or branches

Tools You Can Use

• Cotton thread

• Fishing line

• Fine mesh (stainless or plastic)

• Small dots of aquarium-safe super glue gel (used carefully)

Basic Method

1. Prepare the moss

   • Rinse gently to remove dirt or loose debris.

   • Break it into small tufts – don’t use one big thick clump.

2. Spread thinly

   • Lay a thin layer of Fissidens on the surface you want to cover.

   • Thin is better than thick; it lets light and water reach all parts.

3. Secure

   • Use thread or line to wrap it gently around the wood/rock.

   • Or sandwich it between mesh and then tie the mesh to the hardscape.

   • If using glue, use tiny dabs and avoid smothering the moss.

4. Let it settle

   • Over weeks, it will attach and start to send out new fronds.

   • Once it grips well, you can cut away any visible thread if you like.

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Water Flow and Placement

Fissidens likes gentle to moderate flow:

• Enough to bring in oxygen and nutrients

• Not so strong that it tears the fronds or rips it off the surface

Nice placement ideas:

• On driftwood branches in the midground

• On stones near the base of a layout, like little moss “islands”

• On small rocks or mesh in a shrimp tank, forming grazing patches

Avoid burying it in substrate; it will do better attached on top of things.

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Maintenance and Trimming

Because Fissidens is slow-growing, maintenance is mostly about keeping it clean and not smothered.

Trimming

• Use small, sharp scissors.

• Trim the outer layer lightly if it becomes too thick or uneven.

• Remove loose pieces during water changes so they don’t float everywhere and clog filters.

Cleaning

• During water changes, gently swish the moss in the tank water to lift debris.

• You can lightly wave your hand or a turkey baster over it to blow off dust and waste.

Regular, gentle maintenance keeps Fissidens looking fresh and prevents detritus buildup that can lead to algae.

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Common Problems and Simple Fixes

1. Algae Covering the Moss

This is the most common issue.

Possible causes:

• Light too strong or on too long

• Too much nutrient and organic waste in the water

• Very low flow around the moss

What can help:

• Shorten light duration by 1–2 hours

• Increase water change frequency for a while

• Gently clean moss during water changes

• Add algae-eaters that are moss-safe (shrimp, certain snails)

If some fronds are fully covered in stubborn algae, you may have to trim those parts away. Slow plants don’t recover quickly once heavily smothered.

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2. Moss Turning Brown or Breaking Apart

Possible causes:

• Shock from big parameter or temperature changes

• Long-term neglect + debris buildup

• Damage from rough handling or fish

What to do:

• Trim away brown, dead parts.

• Check filter and flow – is there enough circulation?

• Keep water parameters steady for a few weeks and observe new growth.

Often, if the base is still alive, fresh green fronds will appear again from healthy parts.

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3. Fissidens Not Growing at All

Fissidens is slow, but if you see almost no change for months:

• Check that some light actually reaches it (not fully shaded by other plants).

• Ensure there’s at least basic nutrients in the tank (fish load, or light fertilizer).

• Confirm that temperature is not constantly at the extreme high end (very hot water can stress it).

Sometimes “barely growing” is still normal for this moss, especially in low-tech setups. Think in months, not weeks.

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Fissidens Fontanus with Shrimp and Fish

Fissidens is excellent for natural shrimp tanks, especially with Neocaridina

• Tiny leaves and spaces hold biofilm and micro-organisms making a natural grazing mat.

• Shrimplets can hide and graze safely in the fronds.

• The moss doesn’t sting, poison, or harm them.

For fish:

• Peaceful, small fish that don’t constantly pick or uproot plants are best.

• Avoid big diggers or species that love to tear things apart.

Because it grows slowly, any damage takes time to recover, so gentle tank mates are ideal.

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How I Like to Use Fissidens in Layouts

Some simple ideas:

• As small moss bushes on selected rocks – not everywhere, just a few calm spots.

• On the tips of driftwood branches, like tiny under-water trees.

• In shrimp tanks, attached to small stones that you can move around for cleaning.

In my shrimp tanks, I like pairing Fissidens with a tiny foreground crypt like Cryptocoryne parva, so the moss sits on wood or stone just behind a low, slow-growing border.

Fissidens is easy to overuse, but it looks nicest when used sparingly and intentionally. A few patches are often more elegant than covering every surface.

If you’re planning a new scape, the Aquascape Layout Planner can help you sketch where your Fissidens patches will go before you start gluing.

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Final Thoughts: A Moss for Quiet, Patient Tanks

Fissidens fontanus is not here to impress you in one week.
It’s the kind of plant you add, attach carefully, and then slowly watch as it thickens and shapes itself around your wood and rock.

If you enjoy a calm, steady style of aquascaping – and maybe keep shrimp – this moss fits that rhythm well. It asks for patience, but it gives back a very soft, natural look that feels like a small piece of stream hidden inside glass.