I fine that Seachem reefbuilder doesn't mix well even in less concentrated solutions like 10ml - 1L water. I manually dose.

This is why I asked you in the first place what you are using
I was using Seachem Reef Builder and had to use 8 TBSP per 2L every month or so
I found it would not fully dissolve so I made stirring equipment

I don't worry about it anymore now that I use Randy's 2-Part stuff
It dissolves fully and is about 20% the cost

How did u get 2L to last a whole month! It lasts me less than a week. U must dose a very teeny tiny amount. I bought the seachem when I was still a totally new this hobby. I bought some sodium carbonate from Kelly a while back but was planning to finish the seachem first before I use it. Plus I'll have to adjust the whole amt again n I'm so lazy unless they raise the same lvl of alk with the same amt?.

no they wont , reefbuilder uses alot less than bulk carbonate and is alot stronger, but also costs alot more.

I was dosing just over 100ml per day
With the baked baking soda I am down to less than 80ml per day already so I am finding the bulk stuff is stronger than the packaged stuff