i was thinking.... do you think velcro could hold down the top? like a strip of velcro on each side of the tank, and then on the lid. Velcro's strong, and if your aro jumped, the lid would pull the velcro sidewise so it would be EXTREMELY hard to seperate.
i think a bag of gravel or sand is a better idea than rock or brick. if the aro ever broke the glass top, the bag of gravel is less likely to crack your tank bottom.