Best way to raise ph? Kalk?
 

I have a 4 years old mixed reef 90 gallon with 10 gallon sump. My tank is pretty full and I have started to have ph swings now. I am in the process of setting up a calcium reactor but have been dosing for a couple of years now. My ph is going down to 7.7 at night now so I know I need to do something about it. Is kalk the best way for the ph swings? Would using a doser at night and dosing once an hour be enough to stop the swings? Or would it need to be dripping constantly to keep it stable? I do have an extra aqua lifter so wondering if that would work.

If everything looks happy I would leave it alone mine drops to 7.8 every night with no issue.

Yes, you may be right, however, I have been having issues with my tank being unstable with it's parameters so I am starting to wonder if it is because of the ph swings. I can't get my ca above about 380 and I my magnesium is all over the map. Before, I didn't have to check my doser more than once a week. I am also setting up a ca reactor so my ph will possibly be even lower once I have it running. I have a controller but I don't want to run into issues once it is going.

Kalkwasser is one of many ways. Have a read and decide which one(s) will work best for you. I personally had my best success by drilling a large hole in the side of our house. But that may not be possible for other people. Low pH: Causes and Cures by Randy Holmes-Farley http://www.reefkeeping.com/issues/2004-09/rhf/

I use have a C02 Scrubber set up and attached to my skimmer input. I buy medical grade Soda Lime from a medical supplies place in the US. I did this rather then drilling a hole in the side of my house.

if ph is swinging a lot it is most likely because alkalinity is not stable or at ideal levels. although it does fluctuate at night

True but depending on how tightly closed up your house is this may cause excess CO2 levels lowering PH. my Alk is rock stable but notice PH swings. If I have more people in my house the lower my PH gets. In my case the Soda scrubber solves this and I have personally noticed my corals have been healthier and growth has increased because of it.

Of course everyone's tank conditions are different. What has worked for me might not work for someone else. As in Ryans case he has excellent growth and color despite PH fluctuations.

Ok well if your only wanting to adjust ph then soda ash is your best bet

Did you do Randy's CO2 test that's described in the link provided above? If CO2 is the problem, then trying anything other than reducing CO2 will be fighting an uphill battle. How much calcium and alkalinity are you currently dosing? You may not be able to dose enough kalk to get the pH increase you're looking for. As a sidebar, switching to a calcium reactor will probably lower your pH more. Randy's CO2 test should be step 1 for anyone thinking about messing with pH.

Are you using a controller with a pH probe? If so, has it been calibrated recently?
A few months ago I was having weird results testing for parameters. I updated my test kits but my results were duplicated so I was fairly confident they were accurate. As it turns out my refractometer reading had drifted. The 1.026 SG reading was actually 1.030. Naturally this threw off my other readings too.

When I set up my Apex the pH probe was also out of calibration by fair bit. It was in a box for several years before I installed it so I still don't quite trust it. If your test kits are old and/or your probe hasn't been calibrated in a while, it might be a good idea to make sure they are reading accurately before making any adjustments.