Yep, rubber stoppers, I called them rubber corks and I got them at Ace Hdwe. but naturally the one closest to me doesn't carry small items like that. Had to drive to the big Ace much farther away. I should have posted my long story here but have it under Terrarium Waterfall instead. This tank is driving me crazy but I've learned a lot of "what not to do." I found a plant called Irish Moss...anybody used it before?