Was 8 ish on 3/2 but been climbing since was at 20 yesterday before the water change.
On 3/3 i did start adding Seachem clarity(i know now is Bs and doesn’t help with ammonia) and Seachem fuel (maybe that’s why i had the copper in the tank?)
Is 18 alk a at a point where it is toxic? How do i remove?
18 dKH is too high. Are you adding something that is increasing alkalinity (kalk, 2 part, AFR, baking soda, etc)? If so, I’d stop. How is it being measured?
i check using a Hanna checker. I think i figured it out there, i added reef buffer few days ago to help increase ph.
Should i do a small water change to drop it or just let the tank eat it to come down?
That could do it. How much buffer did you add? If you’re adding buffer, use small amounts in a single use. A little goes a long way. You can always add more if need be. I would continue doing daily water changes. The corals will also consume it, but water changes will normalize it faster. The water change will also help lower your ammonia, nitrates, and phosphates.
Should i do another 5 gals today since i did 10 yesterday?
Yes, let’s see what that does. We want ammonia and copper to be zero and not detectable, respectively, as soon as possible. Once that happens, you can start doing smaller water changes, 1-3 gallons, every day to lower alkalinity, nitrates, and phosphates.