What a box can do
It can provide short-term separation during an observed birth or hold fry temporarily while a prepared grow-out tank is ready.
What it cannot do
It does not replace a cycled tank, stable temperature, filtration, cover or long-term space. Water inside may have poor circulation.
Watch the adult
Pacing, clamped fins, refusal to eat, rapid breathing and repeated escape attempts indicate that confinement is not working.
Prefer planted space when possible
A mature planted tank plus prompt fry transfer may be less stressful than predicting a birth date and confining the female for days.
Have a removal plan
Never leave a fish unattended in a device that can trap, injure or isolate it without adequate water movement.