Welcome to MASA Lindsay! WOW! A 2 metre tank for mahala! Now that's a nice late Christmas pressie!
What are your water parameters like? Have you measured them lately? Do you have a DSB in you tank at all? (I does not seem like you have one in your sump).
A Deep Sand Bed (DSB) is a sand bed that's between 100mm and 150mm deep (can be deeper, but NOT shallower). This facilitates greatly with nitrate reduction. In which case definitely makes the coral pieces/noodles/bio-balls redundant. A DSB is far more effective in nitrate (and actually all nutrient) reduction.
There are SOME people in the world that ONLY use DSB's with algae scrubbers as filters for their marine tanks.
Please let us know how those blennies work out? Are they really algae only eaters? I have seen some in rockpools all along our Indian Ocean coast, and some look like they eat pods, and only some actually eat algae....
Remember - detritus ANYWHERE that's hidden away can and WILL cause nonsens in a marine tank - as it releases phosphates as well as nitrates (phosphates being the major component of nuisance algae's diet)..... So if you have detritus IN or around your rocks, in the corners of your tank, in your sump - you are bound to have problems with nuisance algae.