Within a week, you should notice bubbles in the sediment next to the glass indicating thesand filter is working, within a couple weeks small tube traces should be visible in placesin the sediments near the walls, and small bug populations should be evident. After atwo week wait - and more time is desirable - fish may be added. UNDER NOCIRCUMSTANCES SHOULD YOU ADD "SAND-SIFTING" ANIMALS SUCH AS BURROWING SEASTARS OR SOME GOBIES. These animals are "sifting" the sediment to eat the sandcritters that you need to have thrive. From this point, gradually add more animals upto the desired level.