I use a peristaltic pump (fixed rate 120ml/min) connected to the Aquatronica.  Right now it is set to come on for 1 minute, every 2 minutes.  This provides a flow rate of 55ml/min.  (120ml for the first minute, 0ml for the next minute)  Flow is controlled by varying the time on/off by the second.
  Here's the pump I use.  This CDN company has been easy to work with and delivers promptly.
http://www.omega.ca/shop/pptsc.asp?r...100&Nav=grel07
http://www.canreef.com/vbulletin/sho...t=28436&page=8
  I use a slightly smaller version of the same pump to push water through the Kalk reactor in the exact same way.  For both pumps, I went to RP Electronics and purchased a holding box and power cord to wire them up with.
  For you, the trick is to purchase the correct size of pump.  Measure your current flow in ml/min, then purchase one that is exactly what you want (run it continuously)..or get a larger one and cycle it on/off for adjustable control.
 
		
	
		
		
		
		
			
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				400 gal reef.  Established April, 2007.  3 Sequence Dart, RM12-4 skimmer, 2 x OM4Ways,  Yellow Tang, Maroon Clown (pair), Blonde Naso Tang, Vlamingi Tang, Foxface Rabbit, Unicorn Tang, 2 Pakistani Butterflies and a few coral gobies
My Tank:  
http://www.canreef.com/vbulletin/showthread.php?t=28436