Can get you grayling,but they don't travel well Len...
Tried them years ago in a massive 8ft x 4ft x4ft tank with a load of air stones and jets ,to try and mimic a river....they didn't last a week from memory,same as perch in a tank,chub thrive but f***ing eat everything...
Would like to build a coarse pond in my garden,now the kids are grown up,fill with roach,rudd,perch,ruffe, tench,crucian carp etc