I have 4 peacock gudgeons in my 180 litre tank, 2 males and 2 females. They were supposed to be 1 m 3 f but they were immature when I bought them and one female turned out to be male. Luckily, with a tank footprint of 107 x 45 cm (42 x 18 inches) there is room for both males.
The dominant male is a big fish, he's twice the size of Colin's 1 inch. He breeds regularly with one or other of the females - he's in his tube guarding eggs as I type. He only just fits but these fish like to spawn in tight spaces. There are various 'caves' in the tank, the one he's adopted as his is a length of 1 inch plastic tubing with slate siliconed to it to weight it down and make it look prettier.
I've had the gudgeons for 2 years. I feed the tank flakes (Omega One), pellets (New Life Spectrum) and a variety of frozen food. The gudgeons swim to the surface at feeding time, they don't wait for the food to come to them. Mine definitely eat dry food!
The tank does have lots of hiding places as Colin recommends - I have a lot of wood with plants attached, and water sprite as a floating plant.