Thanks Perseusmom. Well, Bluu didn't murder anyone overnight, and today I got him a 19 litre nano tank of his very own, with a filter and a heater. I've stocked it with plants, and now we just have to wait for it to cycle
. I rinsed the filter in my existing tank, and filled the new tank half with water from the big one and half with water I'd already prepped for a water change, in the hope this might speed things up. Is there anything else I can do? Little boy Bluu is starting to come out of his shell and I'm terrified he'll decide he has to kill my guppies.