Alkalinity Levels are high

Hello all! I have a question for you, but first I will give you some of my tank parameters. Ca= between 250 and 300ppm, alk= off the charts (max range of 300ppm), ph= 8.2, nitrates= 5-10ppm, nitrites= 0ppm, ammonia= 0ppm. I have been reading that magnesium is very important to maintain stability between the water/calcium/alkalinity, but I do not have a test kit (yet) for magnesium. My problem is obviously low ca, but I can't seem to correct it. To get the ca over 300 ppm, I have to dose with calcium every day. (3 tsp of reef advantage calcium). My tank size is 155 gallon, and the corals look ok, but my coralline seems to be slowly dying. How do i lower my alkalinity? BTW, i have identified the problem as being from the make-up water. I use tap water becase it has 0 ammonia, 0 nitrates, and 0 nitrites. However, our tap water come from the tap with a PH around 7.8, and alkalinity that is off of the charts. Perhaps I should just switch to R/O, and slowly dilute the alkalinity.? Please let me know what your thoughts are.
THANK YOU VERY MUCH!!!

 

What is your Alk in terms of dKH?

 

300ppm would translate to a dKH of 16.8.....and it sounds like that's the minimum.

 

I would really switch to RO if I were you for starters

 

Just taking a shot in the dark on this one.......what is the expiration date on your test kits?

 

The min is 16.8 dKH? Where the heck do you keep your Alk at FarmerJohn?
I'd have to say I wouldn't want to see it any higher than 14 dKH. 12-14 is where I keep mine.
I'd question that it would be that high from tap water. I'd vote to re-test it with a RedSea or API test kit, or at least bring it to a LFS if you don't have/can't afford the test kit right now.

 

Expiration dates

Thanks to all that have posted so far! My calcium test kit i Red Sea and it expires February of 2010, and the other tests are Mardel and they expire in March of 2009

 

It would really help to know where your Mag level is. Besides the obvious(Cal), Your Alk/DKH must be really high. What I would do;
1. Stop using tap water and get yourself a decent R/O unit
2. Get your Mag to 1400-1500ppm
3. Lower your Alk/DKh by either doing WC's or just letting it be consumed or dosing Cal every day.

Luna

 

dKH confusion

I think that FarmerJphn was converting 300ppm to dKH, and that is the minimum that I have in my tank. (Since my kit can't go any higher than 300ppm. I think...

 

Pick these test kits up, lotzofish. Don't have to get them from that site, many Petco/Petsmart/LFS will carry them.
Aquarium Water Testing: Aquarium Pharmaceuticals KH/carbonate and Calcium Test Kits