with the ecosystem sump the claims are skimmerless but this is not something I would recomend for 500L I would recomend a Miracle Mud Refeguim with a Bubble Magus NAC7 but do lots of reaserch if this is something you wish to try.
The Inventor of the system is Leng Sy do a google search on Leng Sy Ecosystem and read up
those bubble magus skimmers how do they work? so do you pipes in the intake and out take? only because they look very good and quite cheap (cheaper than deltec ones)
similar sized to the tank ive bougut today, looking forward to seeing what you do