not sure about the lobster, but with the jawfish, mine is on day 5 or 6 in the DT, and he's made 3 differrent burrows so far, and he still only works on them when he knows no people are around. Also, if he starts making a burrow in the front of the tank, resist the urge to shine a flashlight down in it, because that will lengthen the amount of time before he feels secure, and will likely relocate and start all over again.