I bought a reefkeeper and I love it. It has built in timers for your lights and for your ph's.
My fish are not stressed about the ph's turning on and off. It doesnt really phase them at all.
The reefkeeper also has ph and temp probes that display on a digital monitor. It has 8 channels on the timer you can set-up in a variety of ways. I have 4 for lights and 4 for ph's and a return pump. It also knows the difference between pc's vho's and mh lighting. I have the ph's on a cycle of 2 on, 1 off and 1on 2 0ff switching every 5-6 mins. It also has options to turn the ph's off at night for a calm sea effect. It just leaves your return pump on.
It also has a feeding mode where it turns all the ph's and pumps off when you feed so you have less over feeding and it is easier to spot feed.
If you are looking for ph's to have on a "WAVE MACHINE" or timers I would not buy Rio's or the Seio's made by rio. They are not made to turn on and turn off. I had a Seio 820 on the reef keeper and it last about 2 months before it busted the magnet in 2 spots on the impeller. However, I do have powerjet 1200's on it and they do fine. If you have any more questions just let me know. Hope this helps.