Don't have a lawnmower but I do have yellow watchmans, and they are easy keepers. They can be skidish and scoot off and hide at any new outside tank movements, but for the most part they basically set there and watch the world goby. I play with mine by poking a finger at it, and it takes off and dissapears only to come out at another spot and starat to look again. I poke my finger at him there andhe off and comes up where he ws at to begin with. But all hiding is over once I throw a bit of food in the tank........They are not a very active fish but they are interesting. Mine eats anyhting i put in the tank.