Breeding/isolation Boxes

Just wondering if anyone has used a breeding box as either a isolation box for new fish or to help a sick fish where you don't have a spare tank.

I did toy with this idea before when one of my x-ray tetras was fatally ill but ultimately didn't proceed.  In my own case, the fish concerned had catastrophic swimbladder malfunction which was causing him to bounce and catapult all round the tank and, in that unique/unusual situation, I thought being confined in a small container might be distressing for him.  If the sick fish weren't moving much, or had a swimbladder malfunction that might have it lying on its side / upside down but otherwise relatively still, then this would be an ideal solution.

As for new fish:  If it's new fry, I have read of some breeder boxes having holes that are quite large and the fry end up escaping through that and ultimately get consumed by others.  If it's new fish from the LFS, then you wouldn't need this / they may become distressed being in a small container and it wouldn't serve the purposes that a quarantine tank would (ie keeping them apart in separate water to ensure they're disease-free and don't pass on any illnesses to existing tank stock).

In a nutshell, breeding boxes can be very useful in some circumstances, but not all.

For sick fish, I have a plastic tank with a spare heater and filter and silk plants specifically for it - it's stowed away at present but is something like 20L. For anyone reading this and contemplating buying one for such purposes, I would recommend getting one from a LFS such as PAH or MA, not from a homestore - I once bought one from "The Range" but it wasn't practical because the lid couldn't accommodate cable wires, an issue I hadn't foreseen.

The breeder type boxes are exactly as it is described as, which is used to allow a fish to give birth to fry (livebearers) and then keep them from being eaten. I have used such boxes before. I have also seen them used to observe at a closer distance but obviously this is a very short temporary solution.

the link here: https://www.petsathome.com/shop/en/pets/fish-tanks-and-cabinets/aqua-town-kids-aquarium-with-filter-12-litre

is the QT (Quarantine Tank) that I use for sick fish and for preparing new livestock for addition to the main tank. You could also use it as an isolation tank or for breeding purposes. I use this tank with no light but some fake plants, no substrate, a cycled sponge filter and a 25w heater.

It is used on a as required basis and the sponge filter is kept in my main tank running to provide extra support for my main filter when not in use in the QT.