Tahl, you've got a new system running (sort of new). You should expect some algae blooms over the next month or two. In addition, it appears that you've got your fuge light shining directly above the baffles (tough to tell from the pix, but it looks that way), and this could be another factor in what appears to be algae growth.
FYI, the silicone is from Perfecto and is specifically made for aquariums, both FW and SW.
swimmer