Stupid question of the day

[trying4reef]

I have many "dumb" questions that I need to ask but in trying to keep it light I'll offer at most one a day here is todays;
what is Akalinity?
I hear the term and have read that I should be testing for it if I add corals but can't seem to find a definition. any help? in laymans terms please

 

[bacchus_fl]

Alkalinity is also considered the "hardness" of your water. I only tested my water the first time I set up my tank. From what I understand its main importance is that the harder your water is (the higher the alkalinity) the more stable your PH level. The softer your water (the lower alkalinity) the quicker your PH level will drop. As long as you test your PH regularly and use a good buffer your alkalinity and PH should stay at the proper levels. This is a very basic explanation but I am sure you will get several more in depth definitions. Hope this helps!