Hello there, for the silicon work I used masking tape to tape off all areas that were to remain silicon free. For the internal corners, seams, joins, I used a rounded off piece of wood, shaped like a blunt pencil. All pieces were siliconed during the one event. One after another and the internal corners penciled out before the silicon started to cure. I basically just went over and over and over on the internal joins until there was no silicon on faces of the glass surfaces that you see though. The excess silicon is moved out onto the masking tape during this process. The tape was then removed once the silicon had started to cure.
I can only put limited size rock though the top hole. I can fit anything within 140mm x 140mm on any two planes. The rock I have put in the tank looks about the right size for the tank, so it worked out well.
More updates coming soon. Cheers.