you have a few option... place heavy decor on it,... tie it down... boil it ( if it isnt huge)... but really the best thing i've seen/done is drill it to a piece of slate... and cover the slate with your gravel... it hold very very very well
ITS HEAY BUT I THINK ITS VERY DRY, YES I DID PUT IT IN THE WATER, AND ITS 46" BIG. I AM GOING TO BRAEK IT TO SOME LITTLE PIECES, NOW ITS TOO BIG FOR MY TANK, I WILL LET SIT IN WATER A WEEK OR SO,,
THANX
don't soak it in the tank.
get rubbermaids instead.
since some driftwood are tough and will float even after putting weights like stones on them, and then the stone falls off the driftwood and breaks the glass tank or scratch the acrylic, etc.