Refugium Space Help

[Zhain]

I have a 15 gallon sump for my 150 gallon mixed reef display tank. The sump has 2 filter socks then my protein skimmer. There is a space for a refugium before the water runs through a narrow area filled with CerMedia MarinePure 1.5-Inch Sphere Bio-Filter Media before getting pushed back into the DT by the return pump.

My question is what would you use the empty space for between the skimmer and the bio media?

I am thinking about just filling the entire space with more MarinePure bio media. What other suggestions would anyone have, I am open to anything and everything that will benefit the health of the tank.

Thanks!

 

[JDWells]

The best thing I ever did for my 125 was making an upflow algae scrubber. Cheap and easy to make, tons of info out there. It worked way better than a typical fuge with chaeto and the like.