I've been using an Alkalinity test from Aquarium International. It's the first drop -> blue, count drops until it's yellow. Including that first drop, it takes 7. It tells me to divide by 2 - so the unit is 3.5. This number doesn't make sense to me. I got in my API Reef test kit and this has a Carbonate Hardness (kh) test. It's basically the same thing. Only with this test, it takes 10 drops to go from blue -> yellow. According to its chart, this means I have 179 as my score. I did both tests, back to back, twice. Same results as stated above. So I've got a couple questions - so far, this is the test I understand the least. 1. I've read that alk and kh are interchangeable. Is this true? If it is, I will stop with the alk test and rely on the API kh test. 2. The API kh test says that ideally it should take anywhere from 8-12 drops. Do you agree 3reefers? Giving me a score of 179. As a matter of FYI, I will list all scores from my last testing round (yesterday). But I'm only asking for info on the above. (BTW - tank is a few years old, but moved to my house 8/15 (same water, etc.)) Temp 79 <consistent> SG 1.027 <consistent> Ca 400 <mostly consistent> PH 8.4 <I'm getting better at deciphering the colors on this one> Ammonia, Nitrite both 0 <consistent since 9/12> Nitrate 15 <was at 20 since 8/23, seems I'm ending a cycle> Phosphate .5 <first time to run> that's point five. And of course Alk 7 drops or 3.5 after conversion - if I'm converting correctly? But it's been 7 drops since 8/25 when I first got this test. kh 10 drops/179. First time to run it.