Hi Davy,
I’v never heard or read about the possibility of keeping a smaller breeding tank inside the tank of the adult paros. Wouldn’t that be cruel for the paro male ? The canister will remain visible but he won’t be able to reach and guard it in the way he’s supposed to :dry:
Some of us prefer to put the canister with eggs in a seperate tank. I wouldn’t be surprised if they also have a third or even more, bigger tanks for larger juveniles of the same couple. It’s probably the best way to grow up a maximum number of paros.
I personally keep the fry together with the parents untill they’ve reached a certain size. Only then, I move them to a bigger tank where they grow up in group. As for exemple yesterday, I moved 14 young paros of different age from a parental tank. They’ve joined their older brothers and sisters. And yet, today after a serious water change, the parents already seemed quite active again 😉