I run my 4 6025's on 1 seio controller (no problems since they don't pull even half of what it's rated for power wise). I also have an RKII, but I don't run them on it since it's wavemaker completely shuts off power to the PH's. The SEIO controller is similar to a Tunze controller since it reduces the power to the PH but doesn't shut it off completely. Every time I restart my Tunzes after feeding or loss of power, I have to put my kent scrapper in front of at least 2 of them to get them going in the right direction again. I've tried to let them run for awhile to see if they would correct themselves, but they don't. I've had them run in reverse for a day after a power outage.
Big D