Without knowing your bio-load it's hard to say when the media from the HOB
can be removed. I would honestly think you could easily get away with removing it in a few weeks if not sooner after the base rock is implemented. I did not realize you had all the "extra's" and as I said the HOB
will not be the primary source for the bacteria.
What I mean by "seeding" refered moreso to actual critters not the bacteria. Small animal life like amphipods, copepods, mysid shrimp, worms and the like. They will all contribute to a healthier tank. If none of the things you have added thus far contain these things, you would do well to look into it. The LS
that many places sell is primarily wet sand that is claimed to have nitrifying bacteria or even in rarer circumstances actual aniamls. After 6 mo
., the 10 lbs of additional LS
will have colonized the dead base sand by now.
The lava rock will basically do much the same thing as what you will get from other sources. I would just urge caution on it's use as it can sometimes leach impurities into the water. The stuff you have now would have done it by now so so not worry about it.