Hi Hock Meng,
Below is what I think:
- You should be able to remove the right side shelving.
- The center vertical partition is probably designed to support the tank, so I think you should not remove that.
- So what you can do is put in 2 sumps connected with a thick short piping, with a hole drilled thru' the center vertical partition. The connecting pipe has to be thick so that water level on both sump stays the same. Just make sure the seals for this piping is good to prevent leaks.
- Sump 1 can contain: filter sock, skimmer, FR, bio-reactor,...etc
- Sump 2 can contain: refugium, which overflows into return pump compartment.
Have fun.