Yes it is, it is very difficult to have 2 surfaces that are hard (glass and wood) to be perfectly even, any divots or imperfections in the wood could cause the glass to crack. Not sure how many gallons that is but from the looks of it I'm going to say minimum 200, thats almost 1600 lbs, without the weight of the glass, sand, rock, that you are going to put in their. Why take a chance??