the water in the sump seems high.
for the fuge, if it was me:
turn the bulkead fitting around so the white pipe is inside the sump to allow more room outside
the gray main tanks drain line i would use flex pvc and T off a line with a valve to supply the fuge
measure the area to the right and call
Glasscages.com - Home to have a tank made to fit that area, the tank must be higher than the sump, gravity drain into sump.
i doctored your pic to get a closer look, heres a pic of mine. the line from the chiller feeds the fuge with a T to control the flow into the fuge the rest gets dumped into the sump. the fuge drains by gravity into the sump.
or redu the entire under area of the tank and have glasscages make two tanks for ya, both the same size to fit the area. since it seems the tank that is there now is quite large in comparison the area its in.
what are the measurements of the space under the tank?