I don't know if it will help but I made a small pond from a plant trough.........I went on ebay & got some oxygenating plants to create a liveable water environment & also a couple of taller ones that come out the water & shade it. I also covered the top with pond moss to disguise any wildlife from predators. Like you I also put bricks at the side to help them in & out. "Frodo" moved in within the month & has been with us for his 3 years (assuming it's still him!)

here are some links........hope they're useful:

Plants For Ponds at Focus

Royal Horticultural Society - Advice: Wildlife ponds

Paul Bromfield Aquatics - Pond Plants,Aquatic Plants,Pond Equipment