Pond Boss Forums POND CONSTRUCTION Creating habitat CC CAVES

I tried searching but no luck. A few questions that I could use assistance with...
1. I have access to 3 4 foot long concrete culverts. I figure to just roll them in from the edge of the water. Should one end be plugged?

2. I'll soon have over 150 CC in the pond which is fed daily. Is there a good round figure on the number of caves I should install? Initially, I plan to wire two 5 gallon buckes together at the mouth and cut a hole in one end. Attach it to a concrete block and install around the edge.