What can cause high alkalinity?

[carey]

I just setup my 180g a couple weeks ago and used half instant ocean salt and half some no name salt that came with the tank. I just tested the alkalinity and it came in at a little over 12 dkh. I have not added any supplements or even purple up, nothing at all. So, why is my alk so high? That reading is at the top end of reccomended amounts so I'm kinda curious. In all my other tanks they usually settle in at around 8 dkh after a water change with I/O reef crystals and require some soda ash from time to time to keep it that way.

So, what gives? Anyone know?

Thanks!

 

[carey]

No one knows any thing about high alkalinity? lol C'mon guys, I know you all know more than I do so please share. Want to avoid any issues.