Hi Esox-
nice pics of sturgeon/carp/pike in the gallery by the way!
I think the common bristlenose are the easiest of all catfish to breed, as they don't need a water change or anything to get them going, or specialised pH/hardness parameters- all they need is a cave for the male. The fry don't even need special food- thus far they've been much easier to raise than were the Brochis that spawned last year. Don't start with a blackwater species of Ancistrus though as they need really soft water and low pH, and possibly high temperatures. For this reason, go for the tank bred bristlenose- anywhere from £2-£4 for 1" fish, which sounds pretty steep when they breed so easily!