The problem I have is ... My kH is ... around 14.6 dkH; my Calcium is around 470 ppm, and my pH (at its peak) around 8.55. I have already toned down the effluent flow to where you can see separate distinct drops form ...
1. Should I slow down the effluent flow even further?
2. What is the effect of increasing or decreasing the flow of CO2 into the Calcium Reactor?
Hey KM, the two posts already presented have brought up a few of the points I would consider, usage of the alkalinity (low utilization) and your CO2 bubble rate. The effluent rate sounds about right to me for a 190, although with your populations in the tank, it may still be too high. Before you do anything, post your methodology for testing your pH, your alkalinity, and your Calcium. Also, if you use a pH meter, clean the probe and make sure it is calibrated, as much will depend on accurate measurements of the effluent as well as the water column.
Personally, unless the tank presents problems with your inhabitants, I wouldn't do anything to change it initially. The high alkalinity will come down as your coralline algal pops increase, as well as will your Ca as utilization of the calcium goes up. The excesses of both will salt out in the tank if conditions are right (and if they go bad, you will see a tank "snow out" as the Ca and carbonate/bicarbonate combine under the right/wrong conditions to form CaCO3.
Assuming your testing methodology is good and that the meter is clean and calibrated, there are several events that may be occurring that are driving your parameters up (they really are not too bad). Part of the high alk level is that your alkalinity is a product in your 2 column system of excessive dissolution of the aragonite medium by high levels of CO2 (as carbonic acid). The bubble rate that you have would prolly be a little high for a single column system, but here the second column acts to neutralize the excess CO2 such that your Ca prolly is at supersaturation and is precipitating out in the 2nd column as the pH rises from what is prolly around 6.5 to 6.7 to a near neutral at the effluent (this is an estimation on my part based on what your water column presents under the current conditions). The carbonate/bicarbonate portion of the effluent is much more soluble than the Calcium ion portion, and is further affected by existing CO2 in the water column. It will stay in solutiion at its relativly near-saturatioin state even as the pH rises as the column dissolves the aragonite in the second column. This is why your alk is so high and your calcium would still be near 500 ppm.
I would be interested to know what your pH of the effluent is at the point where it enters the tank/sump. Take a small mason jar and capture the effluent where it drips into the tank, place a pH probe in it, and let it run for a few hours (and overflow into the water column) and check the pH. If your pH is more than 6.7 or so, then what we have discussed is the most likely scenario. As you slow down the rate of delivery of CO2, you should see a corresponding drop in alkalinity without much of a drop in your Ca delivery rate. Keep good records of your pH, alk and Ca tank levels as the CO2 rate of delivery is slowed, and allow for 2 to 3 days to pass between each final evaluation, testing at the same time every morning and evening during your adjustment period (I would test your calcium and alkalinity 3 times at each teseting and take an average of your values). When you see a corresponding drop in both your alkalinity and your Ca in the water column of the tank, then you have found the "sweet spot" for the CO2 delivery.
If the critters look good, there is no rush to do this, but it will save you from wasting your CO2. If you had a shorter column (or just 1 column), you would see a drop in your overall pH at higher delivery rates. If you were delivering insufficient CO2, you will see a high er overall pH but your Calcium may be low, but even that will depend on many many variables. With the long column (2 columns), I would think that this is the most likely scenario. You might want to read Randy F-Holmes article in Advance Aquarist for a more detailed discussiion of some of the variables on this
Read the article, and go ahead and adjust your CO2 delivery rate but leave your effluent rate as Rick had suggested. Record the results, and continue twice a day testing for at least 3 days in a row without changing your delivery rate. Make sure to do your bubble rate changes slowly in order to determine the actual effect on your tank. Regardless of what you decide to do, definitely make the changes slowly, and check your equipment and your methodology before deciding to make any major changes.
HTH, many variables, this should give you a starting point.