Sump ideas

I feel that my sump could be made a lot more efficient. I have never changed the configuration - it is the same way I bought it. Here is a diagram of my setup:

The overflow from the DT (actually from a secondary sump housing the skimmer - my skimmer couldn't fit under my tank where the main sump is) comes into the right hand side of the sump through a prefilter (scourer pad) and wet-dry trickle filter. The right hand section contains some scrubbies. The water goes under the first glass panel and into the middle section. Here there are 3 containers of ceramic noodles and crushed coral. The water then overflows into the left hand section where it is pumped back to the DT.

I want to make this more efficient without having to add or remove glass - I am not confident with glass cutting and am pretty poor.
I thought I could move the bionoodle/crushed coral containers into the right hand section - there is plenty of space under the floating scrubbies. Then I could turn the middle section into a refugium, however the middle is only 17cm long, 26cm deep, 30cm wide.

Any other ideas?

 

So I moved the noodles and crushed coral to the right hand section. This section now contains scrubbies, a few bioballs and the noodles & crushed coral under the wet/dry filter.
I put a small piece of Gracilaria hayi in the middle section with a light above. Hopefully it will grow. It seems very difficult to buy macro algae where I live - the hayi is the only one I have seen for sale. Being a red algae, does it require a different light spectrum?
The left hand section of the sump seems so wasteful. It is approx 25cm wide, 30cm long and 25cm high (guessing as I can't find my measuring tape) but only has a 1 pump in it.
Do you think it would be good to add a DSB? Or is this unnecessary (nitrates currently undetectable, although tank only has 1 fish - we recently has a devastating earthquake and 4 days without electricity killed most of my stock).
Would this be a silly idea? :