Breeder Box: A Practical Guide
A breeder box is a small in-tank or hang-on enclosure that isolates fry, pregnant livebearers, or recovering fish while keeping them in the main tank's water.
Overview
A breeder box is a container used to temporarily hold tiny young, eggs, or sick fish that need isolation while they grow or heal. Unlike a separate quarantine tank, most breeder boxes float at the water surface or attach to the side of an aquarium so that the occupants share the same water as the rest of the system.
Why use one
Most aquarium fish show no parental care toward their offspring, so newly hatched or newborn young are easily eaten by adults. A breeder box raises survival rates by containing fry behind a barrier that keeps them out of reach of larger fish while still allowing them to feed and grow.
Types
- Floating models that sit at the surface
- Side-mounted models attached with a bracket or hanger
- Suction-cup versions fixed to the inside glass
How water is shared
Many designs use an air-driven lift, where airline tubing connected to an air pump pulls aquarium water up and through the box. Mesh screens allow water to circulate while keeping small occupants contained, so the box stays at the same temperature and water chemistry as the main tank.
Uses
- Holding newborn livebearer fry until they outgrow being eaten
- Placing a pregnant livebearer until she gives birth, then removing the mother
- Isolating an injured or recovering fish within the existing system
How long fry stay inside
Young typically remain in the box until they are large enough not to fit in the mouths of adult fish. For livebearer species this can take roughly four to five weeks, after which they can be released into the main tank.
Maintenance
Uneaten food and waste accumulate inside the box and should be removed regularly, for example with a turkey baster, and algae may form on the interior walls. Plants or small decorations can be added inside to provide shelter for the occupants, which helps timid fry feel secure and reduces stress while they grow.
Considerations
Because a breeder box is small, the water inside can foul quickly if food is overfed, so portions should be modest and leftovers siphoned out. The mesh openings must be fine enough to retain the smallest occupants; very tiny fry can slip through screens sized for larger young. Adequate flow through the box is also important, since stagnant water and waste buildup undermine the benefit of sharing the main tank's conditions.