Originally Posted by Telek
Well yes, but I don't image that it would take much force with some larger fish swimming around them to dislodge them from the base, and plastic filled with water is denser than plastic filled with air. Just a thought.
Yeah I know, I just meant to point out that even with filling them with water, you still need a way to hold them down. Water alone doesn't do the job, so rather than fill them with water AND secure them another way, it's a bit easier to just secure them the other way. I can definitely see your point about the fish dislodging them, that may require me to get a bit more creative with my engineering of the lego setup. I don't have any fish yet so only time will tell if that's a problem. I'm going to avoid any silicone or permanent fixation because 90% of the fun of legos is rebuilding and changing things around. If the pillar system doesn't suffice, I think the next logical step is to try a fishing line / heavy rock technique. As for now though, the pillars are working.