Indeed. Admittedly, I would feel guiltier if I were to go out and buy new harlequins (somehow seems unfaithful, and hence why I couldn't buy a new shoal of longstanding fish I've had as I want to remember the ones I had for their individual personalities) or even a new species altogether such as ember tetras (my likely next shoal in a two-species, larger-shoals tank, if I can get plant growth in the interim, although not ruled out sparkling gourami). However, I feel less guilty going out and buying additional cardinals as that has been the longstanding intention to have a larger shoal when tank capacity permitted (and, although one did die as a juvenile, the others are - touchwood- showing no signs of anything untoward).
Another factor is the filter media - the beneficial bacteria required to support the fish numbers I had have probably cut back a little, but, if I re-stock in a few days' time, hopefully some mature media from the main tank's filter plus a few drops of Tetra Safestart ought to be sufficient to support the new additions and not adversely affect the main tank occupants, and, if all goes well, then that mature media can be added back into the main tank's filter at the conclusion of the quarantine tank process.
The only problem is that it will likely involve a month of instructions to tread carefully and whisper in the vicinity of the QT plus sleepless nights and worry that I might awake to a fatality during the quarantine phase.
I agree - must be an amazing feeling to breed fish successfully.
[This thread was fit to burst at 193 pages of posts, so have split the topic and created a new thread denoting the year 2020, opening with Sue's post of 3 March 2020. Moderator FCMF. ]