well I pulled a newbie mistake for the first time in a long time. I don't use air stones on a lot of my tanks, I just use the filter for surface agitation, with the exception of my p tanks. Well after moving 2 55g tanks and a 20 around to make room for these new guys, it was about 5 this morning. I had a canister filter and 2 600gph powerheads on the tank but no surface agitation so I add a 30-60 hob filter and called it a night. What I forgot was that the impeller in that particular hob has a tendency to freeze up. You can imagine my horror when I woke up and saw 15 little P's gasping at the surface and turning on their sides. Luckily I have "too much fish stuff" as everyone tells me, so it only took about 30 seconds to have an airstone in the tank and a siphon sucking the water outside. I started pumping water from the 55g next to it, poor rhom must have thought it was the dry season coming on, and managed to save everyone. I'm really glad I was only asleep for 2 hours.
Edit: I just saw where you asked how many, I ended up with 15 p's total from him but only 6, maybe 7, were the macs. He was supposed to hold them until today to give me time to set up a tank for them but after I bought the initial 6 he called around 10pm and said he had sold all but 9 and the he wanted $8 a piece for the rest since someone else had offered him that. I drove over there and got those 9 before he changed his mind again.
Edit: I just saw where you asked how many, I ended up with 15 p's total from him but only 6, maybe 7, were the macs. He was supposed to hold them until today to give me time to set up a tank for them but after I bought the initial 6 he called around 10pm and said he had sold all but 9 and the he wanted $8 a piece for the rest since someone else had offered him that. I drove over there and got those 9 before he changed his mind again.