Egg Binding (Retained Eggs)
🔎 Find by symptom
About this condition
A condition in which a female medaka is unable to release mature eggs normally, causing them to be retained in the abdomen. Contributing factors may include lack of spawning substrate, unsuitable water temperature or quality, and aging.
Common symptoms
- Noticeably swollen abdomen, sometimes asymmetrical
- Female approaches spawning substrate but fails to deposit eggs over multiple days
- Reduced appetite; fish remains stationary near the surface or bottom
- Abdominal pressure may cause impaired swimming balance
Common causes
- Insufficient or improperly placed spawning substrate (plants, wool mop, etc.)
- Water temperature outside the optimal spawning range (approx. 20–26 °C)
- Decline in reproductive function due to aging or individual constitution
- Suppression of spawning behaviour caused by overcrowding or predation stress
Prevention (husbandry & daily care)
During the breeding season, provide ample spawning substrate such as aquatic plants or spawning mops and keep water temperature within the appropriate range. Maintaining a balanced male-to-female ratio and avoiding overcrowding or sudden water quality fluctuations helps prevent this condition.
Related species guide
→ Browse the species guide for this animalWhen to see a vet
Consider consulting a specialist store within a few daysWhat can a specialist store do?
Specialist aquarium retailers can advise on environmental adjustments to encourage spawning. Aquatic-animal-capable practices, where available, may examine the abdomen and suggest management approaches based on the underlying cause.
Related columns
- Beginner's Guide to Setting Up a Planted Tank | Growing Aquatic Plants Without CO2 on Low Light
- Recommended Aquatic Plants for Medaka | Choosing for Biotopes and Indoor Aquariums
- Aurora Medaka Care Guide | Tank Setup to Bring Out Rainbow Coloration and Breeding/Selection Tips
- Mariage Medaka Breeding & Care Guide | Management & Selection Methods to Enhance Lame Coloration