I have a five gallon square shaped glass tank that has bottom and top rims. The stand's surface is a little uneven, so the tank wobbles a little when empty. When it is full, it does not wobble due to its weight. The glass bottom does not touch the stand surface, as the rims protrudes. I have put a yoga mat underneath which helps with weight distribution. I read that this would be a big problem for rimless tanks. Is this a problem with my tank? Do I have to do something more to even it? Thank you so much!