I used to have that film build up on the corner of my display. I usually just scoop it out with a plastic cup. The best explanation I got was that it's a film of protein, an undissolved waste if you will. I'm not so sure if the increase flow will help get rid of it but I would still do it either way.
Your sump looks like it's about 16 to 18" wide. Do you have a small powerhead in this mid chamber? Typically this chamber lacks good flow. This is why I always tell people to add a small powerhead or return pump in the mid chamber to increase the effectiveness of your biofiltration process. You can even do this on the first chamber (the biggest chamber) if you feel like it lacks flow. Especially if you have a lot of live rock or media in there. I learned this from someone one day then when I made this move, oh man.. my tank got so much better! I would give your media stick some space in between each one to help them do their job better. I would give them maybe an inch or at least half an inch then stack the rest of the extra stick vertically against the walls or maybe put them somewhere else in the sump that has good flow.