It depensd on the entertainment center. I had my (either 29 or 20) gallon a coffee table for a long time with no problems, but it was VERY sturdy, and very old. It was probably about 4 feet long, with like 3 thick support things and shelves all the way down. I had the tank centered on the center support. If the entertainment is made of something like particle board, I'd say not. Also, a lot of entertainment centers are only for up to like 70-80 pounds, and a 29 gallon will weigh 300 easily all set up. IF it's for a bigger tv, it might be able to hold more weight. The way to look at it, would you trust 2 of you to be standing on the shelf constantly for however long? Because that's how I estimated weights... It really depends on the way the thing is built though.