nah..my cups are on top of each other..i have slings as well as scorplings all together and all have done fine....it ranges from rufilatas, metallicas,brachys and several nhandu's....all are developing great and molt with regularity never a prob...but thats me and i live in southern cali..so it might be different somewhere else...is it ok to use with stacked cups? The top cups dont get to cold?