All your doing with a reactor is creating carbonic acid. Speeding the effluent flow without increasing the co2 will only decrease the acidity of the carbonic acid. Less acidity means less dissolved co2 and an easier to control reactor.
You're hurting my brain. Please stop making me think
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But you're decreasing the acidity of the carbonic acid in the reactor by upping the DPM. By doing this, you're passing more CO2 to the tank itself.
If you don't change the CO2 rate and you're varying the drip rate, you're changing the quantity of CO2 that will be used to dissolve the media versus the quantity of CO2 that will pass right out the back end of the reactor and into the tank.
Indeed, the pH of the effluent will be higher (and lower in CO2) when you up the DPM but there will be more total effluent being sent to the tank. The net effect on the tank would be a higher CO2 level (and lower pH).
So, you wouldn't want a crazy large calcium reactor because if it were WAY WAY too large, you
could end up just dumping a crap load of unused CO2 to the main tank depressing the pH. If your calcium reactor was this much oversized (I don't think the OP's would qualify as WAY WAY too large), the user might benefit from just adding a smaller quantity of media and setting the DPM, BPM, and pH as he/she would with a smaller reactor.
Here's where I learned how to tune my reactor:
http://www.reefcentral.com/forums/printthread.php?s=&threadid=770351&perpage=478
