Wait, so is your sump running or not running? If it's running, how is the water going through the sump? Are there cutouts in the baffles we can't see?
Wait, does water flow under that first divider?
I'm thinking there's a bubble trap on the first divider, that we can't see, which essentially makes the sump just one giant chamber. If that's the case then you'll have evaporation in all three chambers at the same rate, OR, you don't have the skimmer and returns in their right places.
And are there three chambers or four? I'm also thinking the sump can be backwards. Can you draw us a diagram? Might be an easy fix. :mrgreen: