Well Folks- I don't use a coolant pump whatsoever. Not on my 12/1, not on my 16/1, and not on my 30/2. I thermosyphon everything. Now, I must admit that the 30/2 could use a but more cooling capacity than a 50 gallon hot water tank. Thus, I've commandeered an additional 50 gallon tank to double my cooling capacity.
Keep in mind that by thermosyphoning, you're allowing natural cooling to take place, according to the rate of heat shedding. You DO want that head up towards 180F plus. And thermosyphoning will permit that to happen, sans some darned thermostat. A thermostat, in terms of a Listeroid, is just a widget waiting to cause a problem.