If you don’t mind holes in your wall, why not put the vents and fans in your laundry room behind the tank? Resolves the light bleed issue and potentially noise issue as well.
Cool, I learned something new. My only concern is if the blender can turn the shells into a fine enough powder. I usually use the powdered chalk from homebrew stores. So please share your results.
Think that was a sydney reefer interview with a local oz coral farmer. Dose iron to increase glass algae growth that sucks up n/p and gets filtered out when alage is scraped off.