Nope, no bio balls, dogmatix. Those circles are actually supposed to be heaters, but I didn't label them. I think I should be able to squeeze the skimmer over to the left more so it's in the first compartment. I'm not worried about light getting into the skimmer, the side of the skimmer that would be towards the lights is opaque, the clear side would be facing away from the sump into the door of the cabinet. The collection cup is clear on the lightward side, but that's no big deal.
Yeah, it does make it a slight risk of the pump running dry, but as long as I check the water level every couple days it should be fine. Once it's running we'll see how much I need to top off, that'll be the deciding factor on whether my next purchase is DI and a topoff or a sea swirl. That's part of why I'm wondering if I should make the sump a bit smaller, so I've got room for that kinda thing in the cabinet.
I forgot to put in a section to force the water through some kind of media, but I don't know if I really need that or not. Would just throwing it in the pump section or first section be good enough? I was thinking mostly just for phosban or similar. But then, I was thinking I might just buy a phosban reactor. Maybe I'll try to talk my parents in the US intoo sending me that for my birthday because I don't want to pay $90 shipping on a $50 reactor and $100 of phosban.