Good to hear about the stand. I just cant help but think about the weight of water, glass rock and sand. Thanks for the tip about the ATO. The ATO is the one thing I'm not sure I like. Did you just replace valve or go with a completely different reservoir set up as well?
Thing is with a relatively static downward load, there stands are pretty strong for that weight - its when/if things start to shift that there would be issues. Still, you do need to be careful with piercing the epoxy paint on the stand, because if the inner material gets super wet, then the particle board can swell and lead to some structural issues.
As for the ATO, glad you figured out the problem! I didnt use the Red Sea one for very long at all. I really like the pressure switch and peristaltic setup that came with the Avast Marine ATO and went with that, and a line to a remote reservoir. Ive been running that setup on several tanks in the past eight or so years and its never had an issue. In the past year or so, Ive also been running an Apex ATO, with the optical eyes and float valves, when Ive had to remove the Avast ATO for maintenance. I have a full Apex setup, so I like to controllability and other options of that unit. I think the best stand alone ATO setup that time tested and user friendly is the TUNZE ATO - its well work the money and those things just flat out work.
Ive heard good things about the Red Sea skimmers, and they look quite nice, so hopefully that works out well for you too.