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Is Japanese Cress a Good Plant for Delicate Blue-Eye?

Reviewed by Guidarium Editorial DeskUpdated May 4, 2026
Not Recommended

Japanese Cress is not recommended for Delicate Blue-Eye. The issue is practical, not cosmetic: their preferred temperature ranges do not overlap enough.

Japanese Cress

Cardamine lyrata

View plant profile
PlacementMidground
LightModerate
DifficultyIntermediate
Size40 × 15 cm

Delicate Blue-Eye

Pseudomugil tenellus

View fish profile
TemperamentPeaceful
FamilyRainbowfish
Temp25–32°C
Water TypeBrackish Tolerant

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

74/100

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

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

Layout value

Moderate cover

Japanese Cress helps with good refuge for fry and breaks lines of sight.

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.

Temperature
Japanese Cress15-24°C
Delicate Blue-Eye25-32°C

Overlap: No clean overlap.

pH
Japanese Cress6-8
Delicate Blue-Eye5-7.5

Overlap: pH 6-7.5.

Hardness
Japanese Cress4-15 dGH
Delicate Blue-Eye5-15 dGH

Overlap: 5-15 dGH.

Water and flow
Japanese CressFreshwater Only, Moderate (Standard)
Delicate Blue-EyeBrackish Tolerant, Moderate (Standard)

Flow expectations are close enough for one layout.

Space used
Japanese CressMidground and Background
Delicate Blue-EyeTop (Surface) and Middle (Open Water)
Pressure signals
Japanese CressLow uproot resistance, Delicate leaves
Delicate Blue-EyePeaceful, Nano / Bite-sized (Predation Risk), Hyperactive / Fast Swimmer, and Jumper (Lid Required)

Plant pressure: Low.

Planting value
Japanese CressGood refuge for fry and Breaks lines of sight, Inert substrate is fine
Delicate Blue-EyePlants - Densely covered and Plants - Floating

Shared Tank Conditions

Japanese Cress and Delicate Blue-Eye do not share a clean environmental window, so the pairing is already under pressure before behaviour is even considered.

Both do best with moderate flow, so circulation does not need to be split into competing zones.

Water type can work if the tank stays in the shared part of freshwater and freshwater to lightly brackish water conditions.

Fish Pressure and Plant Resilience

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

Japanese Cress has moderate cover density, low uproot resistance, and delicate leaves. It can also help with fry refuge and breaking up sight lines.

This plant adds the denser cover that Delicate Blue-Eye usually appreciates.

The limiting issue is their preferred temperature ranges do not overlap enough.

Layout Fit

Japanese Cress is a stem plant usually used midground and background.

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

Japanese Cress reaches about 40 cm tall by 15 cm wide and is usually rooted in substrate with inert substrate is fine. 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 fry refuge and line-of-sight breaks. Place it where Delicate 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: Their preferred temperature ranges do not overlap enough.

Best Use Case

Japanese Cress is usually the wrong plant for Delicate 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.

Frequently Asked Questions About Japanese Cress and Delicate Blue-Eye

Is Japanese Cress a good plant for Delicate Blue-Eye?

Japanese Cress is not recommended for Delicate Blue-Eye. The issue is practical, not cosmetic: their preferred temperature ranges do not overlap enough.

Can Delicate Blue-Eye damage Japanese Cress?

Their preferred temperature ranges do not overlap enough.

Do Japanese Cress and Delicate Blue-Eye share the same water conditions?

No. The biggest issue is that their water conditions do not line up cleanly enough for a long-term planted setup.

What does Japanese Cress add to a tank with Delicate Blue-Eye?

This plant adds the denser cover that Delicate Blue-Eye usually appreciates.

What is the main risk in this plant and fish pairing?

Their preferred temperature ranges do not overlap enough.

Editorial Review

Guidarium Editorial Desk

Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.

Last reviewed
May 4, 2026
Last updated
May 4, 2026
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