Sanjay is out of town, but I followed his lead on my tank, so:
- I think maybe we used a concrete bit, but I think a regular would work OK too. Main thing was getting bits long enough (1 foot long).
- Tips: when I did mine, I worked to find a wide, flat, stable one for the base. Sanjay actually used brick pavers for his base stones I think and that's what we used in the HUB. Drill and put them together before you put them in the tank. You can see how it looks, then just lift them off and put them back in reverse order. You can also work on balance this way, so that one side is not too heavy so it would fall over, and you can twist them so they sort of lock together for stability. (Of course, they never fit back exactly the same way in the tank, but you can get close!) Had to experiment a little bit with how much force to use while drilling, not too much or the rock will shatter. I'd say start with a practice rock, and figure you'll lose a couple in the process. Of course, then you have nice rubble.
- Rods were fiberglass (not acrylic, they were too brittle) and we both got them from mcmastercarr,
http://www.mcmaster.com/. They have a jillion things, look under materials - plastics - rods. I think I used 3/8" for mine, I was afraid 1/4" was too thin. I probably needed two or three 5' rods, and they shipped them packed in a nice shipping tube. Rods just cut with a hacksaw.
Good luck! Doing the rock was pretty fun, I think I did it all one day, then redid at least 1/2 of it the next. I ended with some of mine being kind of interlocking, and I like the look. It's easy to do caves and overhangs that way. The one downside of pieces overlapping is that if all the pillars are separate, you can lift off pieces more easily if you ever need to redo a section or take out a rock for some reason.
-- Scott