[Ron, Red Sea recommends 5-15mg/hr dose rate per 25 gallons. I have a 100mg generator that I use on my 210g tank. I seldom use a dose setting >50% when I use it. My ORP levels are stable at about 300mV.]
[Same here. I have a 50 on my 54g+20g sump. Initially, I ran it at 25-30 (into skimmer) to get the ORP up to 340-350. Now I keep it at around 9 and the ORP stays arount there. The small one would probably work for you.]