Sorry for the delay--here's the update. The crayfish in round 1 were a disappointment--as BOD says they don't do squat in colder water, and then they just die but they look like they're sleeping until you figure out that guy hasn't moved in two days and the tub is getting cloudy. Over the span of a couple of months I phased out the crays and replaced them with weather loaches, eel-like fish I was able to buy for cheap from an Asian market. Those guys are hardy and a lot more active.
The nice thing about this simple setup was that I never had to worry about cycling and water quality, because I was turning water over every few days to feed my soil garden. The peppers did great last year, and maybe the water from the tank was a part of that.
I've just graduated to a full-on aquaponics system with a 275 gal. IBC tote for a fish tank (with small channel cat in it), two gravel growbeds, and a sump tank in which I put my loaches (14 of 'em) as well as 9 crayfish that I dredged out of a ditch near my work. The water is fully cycled with zero ammonia and nitrite, and the crayfish are doing a great job of keeping the algae down in the sump, which is only partially covered. I'll miss having the nitrogen-enriched water for my peppers and tomatoes, but I can get the same result--maybe even better--with fish emulsion.
Live crayfish are the secret weapon for kelp bass and sheephead here in southern Cal. ocean fishing. Like the man said, you don't need to worry about oversized bait--the bigger the better. Even lobsters aren't safe. Once I caught a 5 lb. bass with 8 inches of lobster antenna sticking out of its side--with lots of scar tissue, meaning that the food-related injury must have taken place some time before I got the fish!