Can Blue Dolphin (Hap) and Japanese Ricefish (Medaka) Live Together?

🟢Ideal Tank Mates

Yes, Blue Dolphin (Hap) and Japanese Ricefish (Medaka) are ideal tank mates. Both species share compatible water parameters and peaceful temperaments, making them well-suited for a community aquarium. They occupy different areas of the water column, which reduces competition for space. A minimum tank size of 570 litres is recommended.


At a Glance

Blue Dolphin (Hap)

Cyrtocara moorii

Japanese Ricefish (Medaka)

Oryzias latipes

🐠Family Group
Blue Dolphin (Hap)
Cichlids - African
Japanese Ricefish (Medaka)
Killifish
Temperament
Blue Dolphin (Hap)
Semi-Aggressive (5/10)
Japanese Ricefish (Medaka)
Peaceful (2/10)
Temperature
✓ Compatible
Blue Dolphin (Hap)
24–28°C
Japanese Ricefish (Medaka)
10–28°C
pH Range
✓ Compatible
Blue Dolphin (Hap)
7.5–8.6
Japanese Ricefish (Medaka)
6.5–8.5
Hardness (dGH)
✓ Compatible
Blue Dolphin (Hap)
10–25
Japanese Ricefish (Medaka)
5–25
Water Type
✓ Compatible
Blue Dolphin (Hap)
Freshwater Only
Japanese Ricefish (Medaka)
Brackish Tolerant
Flow Preference
✓ Compatible
Blue Dolphin (Hap)
Moderate
Japanese Ricefish (Medaka)
Low
Min Tank Volume
Combined: 570 L
Blue Dolphin (Hap)
475 L
Japanese Ricefish (Medaka)
19 L
Swimming Level
✓ Different zones
Blue Dolphin (Hap)
MiddleBottom
Japanese Ricefish (Medaka)
Top
🏷️Behavior Tags
Blue Dolphin (Hap)
Digger (Disturbs Substrate)Hyperactive / Fast SwimmerAggressive to same species/look-alikes
Japanese Ricefish (Medaka)
Nano / Bite-sized (Predation Risk)Hyperactive / Fast SwimmerJumper (Lid Required)Fry Predator

Behaviour & Temperament

Blue Dolphin (Hap) is a moderately assertive species (5/10), while Japanese Ricefish (Medaka) is peaceful (2/10). This modest difference means Blue Dolphin (Hap) may occasionally assert dominance over Japanese Ricefish (Medaka).

In terms of spatial distribution, Blue Dolphin (Hap) prefers the Middle (Open Water) and Bottom (Substrate) zones, whereas Japanese Ricefish (Medaka) occupies the Top (Surface) zone. Because they use different levels of the water column, territorial disputes are less likely and the tank will appear more balanced.

Worth noting: Japanese Ricefish (Medaka) is a known jumper, so a tight-fitting lid is essential.

Water Parameters

The safe temperature window for both species falls between 24°C and 28°C. Aim for the midpoint of this range (around 26.0°C) for optimal comfort.

Both fish can tolerate a pH between 7.5 and 8.5. Maintaining a stable value within this band is more important than hitting an exact number.

For general hardness, the shared comfort zone is 10–25 dGH. Regular testing will ensure conditions stay within this range.

Tank Setup

To house Blue Dolphin (Hap) and Japanese Ricefish (Medaka) together, plan for an aquarium of at least 570 litres with a minimum length of 150 cm. This accounts for the larger species' space requirements with an additional 20 % buffer to reduce territorial tension.

Providing a mix of open swimming space and sheltered areas with rocks, driftwood, or plants will keep both species comfortable and allow natural behaviour.

Specific environmental needs for this combination include: Sand (Sifters), Smooth Gravel (Sensitive Barbels), Plants - Densely covered, Plants - Floating. Meeting these requirements will help both species thrive.

Both species do well with moderate (standard) water movement, so a standard filtration setup rated for the tank volume should suffice.

Frequently Asked Questions

Can Blue Dolphin (Hap) and Japanese Ricefish (Medaka) live together?

Yes. Blue Dolphin (Hap) and Japanese Ricefish (Medaka) are considered ideal tank mates. Their water parameters, temperaments, and behaviour profiles are well matched for a community aquarium.

What size tank do Blue Dolphin (Hap) and Japanese Ricefish (Medaka) need?

A minimum of 570 litres (tank length at least 150 cm) is recommended. This provides enough space for both species to establish their own areas and reduces the likelihood of territorial disputes.

What water temperature is best for Blue Dolphin (Hap) and Japanese Ricefish (Medaka) together?

Keep the aquarium between 24°C and 28°C. A target of around 26.0°C sits comfortably within both species' preferred ranges.

Are Blue Dolphin (Hap) or Japanese Ricefish (Medaka) aggressive?

Blue Dolphin (Hap) is moderately assertive (5/10) and Japanese Ricefish (Medaka) is peaceful (2/10). Their similar temperaments generally lead to a peaceful coexistence.

What pH do Blue Dolphin (Hap) and Japanese Ricefish (Medaka) need?

Both species overlap in the 7.5–8.5 pH range. Consistency is key — avoid sudden swings, and test regularly to stay within this window.


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