Alkalinity...

[Jeeper]

I will have to say since I have been dosing I have no issue with keeping up with it in my DT where my coral are. For some reason though without adding something to raise the alkalinity in my other tanks it gradually lowers. I am using reef crystals and I have tested my alk in my change water and it's like mid nines or low tens (best I can remember as I didn't log it just checked it a couple times and it was within specs so I didn't worry about it). I have not tested my RODI water but I am wondering if that is what is lowering my alk when it tops off my tanks. I have a FOWLR that the alk creeps down in, and a QT bare bottom couple pieces of pvc that the alk slowly creeps down. I didn't have anything in QT for a month or so and I tested before adding some fish and it was 7.2 (I use Salifert test kits). I have a ATO on this tank as well. Its been a long time since I had chemistry class so I am not sure how the RODI water could buffer the tank water down... I don't know but I would like too...

 

[Luke Schnabel]

Unless you have a coral QT tank I wouldn't bother with it. But in a FOWLR you'll still have coralline algae growing and that takes up calcium and alk.

 

[Reeflogic]

I'm sure you've read this one, but just in case you haven't!

http://reefkeeping.com/issues/2004-05/rhf/

Maybe you can find the answer in here!