100ml Last more than 60 days for a 250L tank.
For normal and colorful corals: 0,5 ml / 100 L / day
If the corals are light-colored (not brown or creamy) 1 ml / 100 L / day Xtra (not Xtra special).
Add directly to the tank into the streaming.
Xtra is the right one for most tanks with normal to very good coloration of the corals, but also creamy and brown colors.