[amoreira]

My DT pH ranges between 8.3 evening and 8.5 daytime with alk running at 10 dkH. I find higher alk tends to reduce this range and lower the levels (e.g. 8.2 to 8.4 when I'm running alk at 12).

pH varies with the amount of free CO2 and other organic acids in the water column. I find the following will help increase your pH (in order of importance).

1. Don't overstock the tank. Too much fish emit CO2 and other acidifiers.

2. Lighting, more intense lighting gives plant life in your DT energy to produce oxygen and reduce CO2 levels, which elevates pH. For my 180 gal I use 3x250 Watt MH + 4x80 Watt Actinic T5's. For the evenings I use a refugium with macro algae + T5's to sop up the CO2 from the DT and avoid the pH dropping too much.

3. Tons of aeration. Use a big protein skimmer and direct the sump return into a small area in the sump where air is mixing well with the water.

4. Frequent water changes (10% per week).

A well controlled calcium reactor will help stabilize alk and pH. It won't raise the pH. In fact it will do the opposite. I've heard of some setting up a pH controller for the DT using a dosing pump with kalkwasser or caustic soda solution. I don't have any experience with this. I'd try 1..4 first before doing this.