Fish and invert gut bacteria, the stuff that comes in on frags, snail/crab shells, etc. is going to be better than what you get in a bottle. You might even get some small worms, pods, starfish on a snail shell. Hard to replace the larger stuff that comes in rock, so keep trying or get a scoop of sand from a local reefer with an established tank - we used to give out sand to new folks like sourdough bread starts.
