I have begun to jar on this date. I had 11 jarred fish on that date, 1 of whom is an agressive female, and 1 of whom still looks like '4 week old' who didn't get the chance to eat.
The jars are about 5-6 liter, and the fish can't get bored nor lonely, as they can see their neighbours and they flare a lot (don't worry, when I think they flare too much, they will get a card in between them)
They weren't stressed at all when moved.
Don't worry about heaters, they live in front of my room's windows and get sunlight, plus my room temperature is really warm.