I run Dolphins and Mags. Never had a problem with either. I have a couple mags running externally one had a small leak once, but after I cleaned it and put a little vasaline on the seal it works perfectly. All pumps need some maintenance from time to time. If you want them to run good and last long you need to clean at least once a year.
I have never had a problem with the dolphin ampmaster 3000, and it is a much better pump than the iwaki I had. It is strong, quiet, and efficient.