I didnt experiance an alkalinity burn on an acropora until my alkalinity shot up to +20dkh due to having too much flow through a calcium reactor. The flesh just pealed off the acro almost instantly. I havent lost anything like that while keeping my alkalinity in the 11dkh range.

Every tank is different, but have you tried a lower dkh? I rarely hear of anyone having good results at that level. What kind of salt do you use?

Hmm..comments are interesting. The DkH of sea water is 7.5. Because I run Ultralith I have to keep it around that mark. I have tried raisng my DkH even 1 point I found I was tossing in a lot of Carbonate. I find it hard to even consider a Dkh of 9 as trying to raise it that high would probably throw my other prams out of wack. For those who have consistently high DkH I wonder if it isn't the salt that is doing it or not using RO/Dionized water for make up.

I like to run with a DKH of 9 just because I don't test very often and when my corals (and coralline algae) go through a growth spurt, alk and cal levels drop fast.
At 9 DKH I have a little bit of leeway before it drops disastrously low :redface:

Hi Marie
What do you think is causing this rapid growth in your tanks? That only thing that I can figure out that would drop your carbonate level that fast is clams.

Thanks to my regal angel I have no clams in this tank...coralline algae and corals are the only calcium suckers that I know about in there

With my 150, my SPS grew so fast that I couldn't give away frags. My Ca was about 400ppm, and alk was anywhere from 8 to 11. Mg never got tested.
I used a large Ca reactor, which I suspect helped a lot, and 2x400w Radiums.
In my current tank, values are mostly the same, although I fight with my reactor (hence, and with alk) and Mg is ~1400ppm. It's been running almost a year and I have hardly any growth.
I doubt I've had enough growth in this year to match what I used to get in a month. So personally, no idea what makes them grow like weeds.

I do have colors like I never had before, so it's a decent trade off.

fwiw, it takes a lot higher than 13Dkh to burn corals, I maintained my alk at 13.2 for about 2 years. I found colors were more vibrant and growth was accelerated. if the alk fell below 11, I would know from the look of the digitata as its color would dull a little.

now it is good to see people trying to quote NSW alk levels but realy who cares :mrgreen:, what good is quoting NSW levels if you don't follow them all. a Ca level of 450 is definatly not a NSW level, Mg of 1400 is close but a little high for the average, but hey, I like a elavated Mg also.

my best growth and color was at 82 degrees, 380-400 Ca, 13.2 DKH Alk, 1350 Mg, 7.9 Ph, zero nitrate/nitrite/amon/phosphate and any others I can't think of right now. I used AB10K 250watt SE bulbs run by M80 ballasts, on home made reflectors.


Steve

I have a problem with low pH. If I let my alkalinity fall to ~8dkh my pH falls to around 7.6 at which point my controller shuts off my calcium reactor and sounds an alarm. So I have to keep my alkalinity in the high acceptable range for the sake of my pH.

However, if it wasnt for my pH problem I would aim to keep my alkalinity in the ~8dkh range as it seems to be more natural based on what I've read.

I use both Seachem Reef Salt and Instant Ocean. 50/50

I agree with you, every tank is different. Thats sort of why I posted in this thread in the first place. The question of 'which DKH is best for growth' seems kind of silly to me because everyone will have their own reasons and experiences that make their preference different. But rather than flat out saying that I thought I'd just state my side and let the questioner figure it out on their own. Obviously a dkh of 8 for me wouldnt be very good if it meant my pH would be 7.6

I think it's safe to say that as long as you're in a range, you're fine. Same as Ca. Anywhere between 360 and 450 will be fine.
Alk between 7 and 11 is where I aim, and as long as you don't fall too low, you should get good results in coral growth.