the back chambers of my nano cube leak from the inner chamber directly to the return pump chamber completely bypassing the chamber where the skimmer and cheato are located. so i drained the rear of the tank and cleaned out as much as i could but the chambers are far too small to completely clear off every little bit. i am just sealing the edges of the partitions, its not structural. does it really need to be a completely clean surface to just to get a good seal? there is still a bit of coraline algae and some tube worm remains. i was able to get all the "gunk" out though.

thanks!

if you want a leak proof seal, you need it to be relatively clean.