Whats the difference ??

brownsalt92 · Jul 23, 2015

Whats the difference between ph and alkaline? Test what kit to use?

yeah2311 · Jul 23, 2015

pH is the acidity or basic of the water. pH of 7 is water and considered neutral, so when your tank is at a pH of ~8 you are slightly basic. If you go too high of a pH it will burn your skin and the scales of your fish much light you would from an acid.

Alkalinity is the hardness of the water. Basically it breaks down to the amount of calcium carbonate (if I remember correctly) is in your water. One way people think about this is if your tap water is soft or hard. Soft water will make your skin feel a bit slimy and like there is a layer of soap, where hard water will dry you skin out over time and leave calcium salt deposits on shower heads and such. People will get water softners if their tap water it too hard. In the reef tank you need the hard water for the corals to utilize the calciums to build their exoskeleton.

I personally use the Red Sea test kit, I believe it is more accurate than other kits out there, but I know several people use the API tests.

Righteous · Jul 24, 2015

Just to clarify, usually when Alkalinity is referred to in the reef hobby, it can mean two related but slightly different things. Alkalinity generally means water's capacity to neutralize an acid. So as this might relate to pH, it would be the water's resistance to acid causing the pH to drop. When we test for alkalinity with our test, what we are actually doing is testing this capacity.

However, most people equate Alkalinity with Carbonate Alkalinity, which is a measure of the the presence of carbonate and bicarbonate ions (this does not include calcium!). So people often list their Alkalinity in dKH which is specifically carbonate alkalinity. Reefers care a lot about carbonate alkalinity, because along with calcium, corals require carbonate to form their calcium carbonate skeleton. This is what reefers usually care about more than the waters ability to neutralize acid.

In order to test calcium levels for coral you'd also need a separate test kit, and this would not be tested by an Alkalinity test kit.

pH can also be important to test. Chronic low pH (7.8 or lower) can interfere with coral calcification. However, generally you're better off testing for Alkalinity and Calcium to start with. Keeping those levels in place, usually keeps your pH in place as well.