Hello Fellow fish keepers

I have a question that i have not been able to answer in as long as i had my tank. It's a second hand salvage with an all in one build.
BUT i'm not sure and can't find any info on how to maximise the space behind for a reef.

tank.pngHow i do it is : in 4 i have my heater and in the baskets in 6 have sponges on top and filter below before the return.

i have live rock in the tank and everything is running smoothly ( algae is to be expected as i don't follow up regularly on my WC due to lack of time) there is a low population of fish ( 6 small ) for the 200L tank.
Water is home made and all parameters are within the norm.

My question is more, how can i improve and use up more of this filter. i want to offer the best for my tank and though about adding extra media in the back or more. maybe even have a nice place for pods to grow behind and flow back into the tank. I'm not sure Click here to enlarge
what are your experiences and ideas. There is no bad idea or answer

thanks all Click here to enlarge