I'm always picking up a bit of base rock. Whenever my LFS
has some good looking dry pieces I grab them. I must have 150lbs of rock in a tub. Always planning for that next tank...bigger and better!!! I agree with what everyone has said, try and stay away from the canisters if you can. I just use a 20g and a 10g with a 75g wet/dry (no bioballs or sponge) with my skimmer for filtration. The 20g is my fuge with the others just for water volume. If you have a 100g tank and stand you should have room in the cabinet for a sump and fuge. Good luck!!!