[smokinreefer]

Well, thanks for that because my intention was to use it for levelling.

My sump is a concept aquariums sump with a piece of plywood glued to the bottom pane.

I slid the tank to where it will be situated and the concrete floor is raised right across the center width of the sump.

Should I just slide shims under?

Or is a self levelling skim coat of concrete really what's needed?

Thanks