Is Water Fern a Good Plant for Blue Back Blue Eye?

Reviewed by Guidarium Editorial DeskUpdated May 2, 2026

Not Recommended

Water Fern is not recommended for Blue Back Blue Eye. The issue is practical, not cosmetic: they are adapted to different water types.

Water Fern

Azolla filiculoides

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PlacementFloating

LightModerate

DifficultyBeginner

Size1.5 × 2.5 cm

Blue Back Blue Eye

Pseudomugil cyanodorsalis

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TemperamentPeaceful

FamilyRainbowfish

Temp22–30°C

Water TypeBrackish Required

Quick Decision

A plant can be technically compatible with a fish and still fail in the actual tank if the fish digs, chews, needs denser cover, or uses a different part of the layout.

Overall fit

62/100

The fish is likely to outgrow, uproot, or out-pressure the plant.

Water match

Limited overlap

One or more core water ranges does not overlap cleanly.

Plant pressure

Low

Blue Back Blue Eye is not flagged as unusually hard on this plant.

Layout value

High cover

Water Fern helps with provides surface cover, good refuge for fry, good refuge for shrimp, good grazing surface, and useful spawning site.

Plant and Fish Fit Notes

Use these signals to decide whether the plant is doing useful work for the fish, or whether it is only surviving beside it.

FactorWater FernBlue Back Blue Eye

Temperature

Water Fern10-30°C

Blue Back Blue Eye22-30°C

Overlap: 22-30°C.

Water Fern5-8

Blue Back Blue Eye7-8.5

Overlap: pH 7-8.

Hardness

Water Fern2-15 dGH

Blue Back Blue Eye10-30 dGH

Overlap: 10-15 dGH.

Water and flow

Water FernFreshwater Only, Low (Still Water)

Blue Back Blue EyeBrackish Required, Moderate (Standard)

Flow expectations are close enough for one layout.

Space used

Water FernFloating

Blue Back Blue EyeTop (Surface) and Middle (Open Water)

Pressure signals

Water FernLow uproot resistance, Delicate leaves

Blue Back Blue EyePeaceful, Nano / Bite-sized (Predation Risk), Jumper (Lid Required), and Hyperactive / Fast Swimmer

Plant pressure: Low.

Planting value

Water FernProvides surface cover, Good refuge for fry, Good refuge for shrimp, Good grazing surface, and Useful spawning site, No substrate required

Blue Back Blue EyeDriftwood (Digestion/Hiding) and Sand (Sifters)

Shared Tank Conditions

Water Fern and Blue Back Blue Eye do not share a clean environmental window, so the pairing is already under pressure before behaviour is even considered.

Their flow expectations are close enough to combine: Water Fern prefers gentle, low-flow water, while Blue Back Blue Eye prefers moderate flow.

Water type is a serious mismatch: Water Fern is listed for freshwater, while Blue Back Blue Eye is listed for brackish water.

Fish Pressure and Plant Resilience

Blue Back Blue Eye does not put unusual pressure on this plant compared with harder fish-plant combinations.

Water Fern has high cover density, low uproot resistance, and delicate leaves. It can also help with surface cover, fry refuge, shrimp refuge, grazing surfaces, and spawning sites.

Its structure adds useful refuge value beyond the normal visual role of the plant.

The limiting issue is they are adapted to different water types.

Layout Fit

Water Fern is a floating plant usually used floating.

Blue Back Blue Eye is a rainbowfish, so the pairing works best when the planting style supports how that fish uses space and cover.

Water Fern reaches about 1.5 cm tall by 2.5 cm wide and is usually free-floating with no substrate required. That makes placement and anchoring more important than simply adding a larger bunch of stems or leaves.

In this pairing, the useful plant values are surface cover, fry refuge, shrimp refuge, grazing surfaces, and spawning sites. Place it where Blue Back Blue Eye can actually use that structure instead of hiding the plant where it cannot do much.

Practical Recommendation

For most keepers, a tougher or better-matched plant is the smarter choice. If you still try it, test with a small amount first and be ready to move the plant before it is badly damaged.

The decision should center on this signal: They are adapted to different water types.

Best Use Case

Water Fern is usually the wrong plant for Blue Back Blue Eye if your goal is a stable display tank. The issue is rarely one dramatic failure on day one; it is the steady mismatch between what the fish does in the scape and what the plant needs to stay attractive long term.