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Originally Posted by goodfortune
I've stopped running my Ca reactor as well, and my pH has gone from 7.8-8.0 to around 8.28 (night) -8.37 (day). I have a Kalk reactor that replaces ~2-1/2 GPD, but I still have to dose Part 1&2 to keep Ca and Alk w/i range. I've never had a problem with algae, but I was not getting the growth I was expecting.
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Not to pick on Michael, but the biggest problem most folks have when running a Ca reactor is that they dose WAAAYYY too much CO2, and end up trying to make changes to the delivery rate based on bubble counts without a pH controller or expect changes they made yesterday to show up as completed system changes by today.
THIS will just not happen.
The rates of changes performed with CO2-based calcium reactors may take up to 4 days to show up as completed system responses in terms of pH, total alkalinity, and calcium levels, and may take up to a week for the final numbers to stabilize. This takes even LONGER if your delivery rate is close to the coral consumption rate in a system with large populations of
hermatypic corals. This is why it is so important to make a good guess at your rate of CO2 and closely monitor (maybe even chart the values 4 times a day) your pH values when dialing in a
calcium reactor. They provide the best form of calcium and alk supplementation (not to mention trace substances that are part of the aragonite medium), so long as there is not an excess of CO2 being delivered to the water column. One of the ways to determine this is to measure the pH of the effluent from the primary reactor column in a closed system manner (pH probe inserted directly into a section of the delivery pipe without exposure to the atmosphere. This prevents degassing of the CO2 which will change the pH value to misrepresent a lower CO2 content.) pH values should be a consistent 6.7 when leaving the primary column for good levels of calcium and alkalinity delivery, while still maintaining appropriate water column values for pH. Delivery of the effluent into rapidly flowing water will also help degas part of the CO2 content while conserving Ca and alk delivery. Even better still is to use a pH controller for the solenoid of the CO2 gas regulator, as this then becomes a matter of keeping the reactor full of media, the gas tank full of CO2, and testing the probe once every few months. With controllers I heartily recommend that you keep a second pH probe and meter for the water column placed upstream from the reactor effluent.
If need be, you can use a kalk reactor to add even more Ca and alk, and the kalk reactor will help to capture the CO2 in the water column as alkalinity to further stabilize the pH swings, but this really shouldn't be used just to correct for a calcium reactor that is out of adjustment ('cuz CO2 is expensive!) On the Pinpoint pH controllers, you can use a litermeter connected to the high end pH range control to prevent kalk delivery if the pH climbs above 8.4, although most folks just use a level control backup and run the litermeter kalk as automatic top off. However, unless the calcium reactor cannot keep up with the Calcium and alkalinity demands by itself, the additional use of kalk only increases the rate of abiotic precipitation of calcium carbonate solids on pumps heaters, and precipatatory events in the system.
The main point I'd like for folks to take away from this post would be that pH issues are usually an indication of excessive CO2 if your pH is chronically low and your system's inhabitants start to show the effects. Another signal that excess CO2 is an issue is the problematic appearance of nuisance algae, especially if everything else that causes nuisance algal blooms (bulb age, nitrates, phosphates, heavy feeding schedules, poor detrital control, inadequate exports, etc.) is in check. CO2 is half of the formula for photosynthetic CHO production, so supplying excessive amounts of CO2 to the water column may be the trigger that starts algal outbreaks when every other cause is marginal.
Be cognizant of the signals of excess CO2 delivery when keeping a Ca reactor, and act accordingly. If you use a pH controller, make sure to test the function of the probe every 45 to 60 days with the borate test, and when the reactor media gets to the last 1/4th of the chamber, start thinking about replacement. I hope this makes it a little easier to understand the issues associated with these great devices, they are much better for out corals than 2 part supplements or the use of buffers and calcium boosters. Once the water column is stable, the use of extra supplements should be limited to correcting imbalances in the water column, rather than regular use as a reactor adjustment crutch.
HTH
