Bacteria cannot colonize on the artificial rocks as they are hollow, not porus.
hollow meaning water will fill up the artificial rocks. This water in the rocks gets really stale after a couple of months as they do not get circulated.
But as long as you place these fake rocks in the tank and do not move them, the water in these fake rocks will not leak into main tank and everything should be fine.
FOr a start, you can move some LR into the sump. then put artificial rock inside.
after a while, remove the other pile and place the other artificial rock.
if want to be kiasu, you can leave the LR inside the MT too and take out 2 pieces every alternate days.
just bear with the unsightfulness for a few weeks.
If biohomme is suppose to do as claimed, you should be ok.
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might be going LFS on Friday... wanna join us and hunt for nice LR?