IMO; It is best to QT Lionfish separately from other fish.
@Lionfish Lair may have better input.
Sorry, I missed this.
One thing I will say, if you only have the one QT and it's either everyone in the "pool" or nothing at all.... throw them all in together. It's definitely better for there to be one fish per QT, but is it better for someone to have three (for example) uncycled QT tanks going? Which is there less chance for failure.... "the inappropriate community QT" or too many QT tanks at one time to handle?
Pros and cons....
Pro multiple tanks
- fish cooties aren't mixing
- if one fish needed treatment, an asymptomatic fish wouldn't have to endure unnecessary treatment. Treatments of any kind are tough on fish, so if they don't need it, avoid it.
- the best time to convert a lion to frozen food is during the QT period. That's a lot of "messing around" in the tank and can stress fish. The butterfly would have had to endure stress unnecessarily at a time when it too is trying to adjust.
- less bioload, better water quality.
Con multiple tanks
- it's multiple tanks!.... it can be difficult to handle, as something could be going wrong in each of them, instead of just one. Water quality could suffer.
- if multiple fish need the same treatment, there's greater expanse and labour to medicate multiple tanks.
It's easier to have a butterfly with the lion than another lion or scorp. But a 10g is not a place for training a lion, as that's a lot of bioload fluctuations.
I'm dealing with the con of a single QT tank right now. I need to remove one to treat the other. That means delays in treatment. Pooey.