Alkalinity : What dKH do you target and why?

There are some indications that higher alk levels can increase the speed that coral can produce new skeleton thus increasing the growth rate. There are potential problems with keeping it that high though, such as an increase in the rate of abiotic precipitation (precipitate forming on heaters/powerheads etc), you also may run into issues with your alk at a higher level if you also use kalkwasser, you may have trouble keeping your pH low enough.
There is less margin for error at the higher levels, if you get a spike in alk levels you can get a "snowstorm" where calcium carbonate precipitates out suddenly as it hits the breaking point which can cause large swings in alk/calcium as it precipitates out.
Keeping it on the low end is not necessarily a bad thing though, for one thing, depending on your pH you can see a much better growth rate than you would expect for the alk level.
http://www.3reef.com/forums/water-chemistry/low-ph-may-not-end-world-75962.html
Also for people running ultra low nutrient systems (bacteria driven like prodibio/zeovit/vodka/carbon dosing) lower alk levels are generally recommended otherwise some people see negative effects on their coral like "burned" tips on acros.
I think some people just go with lower levels because it's easier to maintain based on what their salt mix starts out at as well.

Just some of my thoughts on the matter.

 

This varies entirely based on the coral load. Your alk will not vary unless a coral or some other calcareous organism uses it up, it doesn't vary like pH does.
Some people with lots of soft corals will barely see a fluctuation over the course of a week, while a full SPS system can use up several dkh worth of alk in a day.

 

My tank is still new. Started November 2009. I only have 12 small frags and 4 fish.

My pH is always in the 8.0 to 8.2 range. dKH is alway right around 9.

I felt like my pH is low but wasn't sure how to raise it. I am using BRS two-part dosing. I was thinking of increasing the dosage on Alk to raise the dKH to 10-11, but wasn't sure of the impact on pH or if I should just leave it alone.

M

 

That's a normal range don't worry about it. That's the range my tank runs at and I wouldn't alter alkalinity just for pH, personally. Read the thread I linked before about how low pH isn't necessarily bad for more info about it. Also Randy Holmes-Farley has a great article on reefkeeping.com about low pH you should be able to google for that as well.

 

Thanks. Tank is covered because I have jumpers....

Will leave as is.

M

 

I am running at 76 degrees now. Airstone in my fuge maybe?? How does one increase oxygen levels??

 

If you have a skimmer I don't know how much benefit you're going to get there's a test to see if your pH will be affected by better aeration, measure the pH then take a cup out, run it with an airstone for a bit outside or in a very well ventilated area then measure the pH again, if the pH raises then you would benefit from better aeration or better ventilation in the tank room. Also, you could do the same test in the same room, just take a cup out and run an airstone in it for a bit to see if you could stand for better aeration maybe due to having the tank covered.

Also just to clarify I don't believe that oxygen levels affect pH, just CO2 because CO2 is acidic, O2 not so much. You can test for dissolved O2 with a test kit I believe.

Having a sump and skimmer might be enough.