Welcome to R2R. Great family of support here
I don’t know about thickness but be absolutely certain the aluminum mold side the glass is on the outside of the tank to prevent permanent alkali glass corrosion. See Tidal Gardens YouTube video.
For float glass it is in an iron base....glass floats in an iron bath to prevent sticking and also aid in a uniform thickness. For the most part glass is typically labled which is the iron side. Work at a glass facility. What I would do is specifically ask them to tape the iron side if possible when making the cuts for you....depending on where you get the glass they will do this for you so you dont have to try and figure it out yourself. This is only if the glass comes from a float plant. Some glass does not and is a melted process with nothing to gauge thickness but a press that it gets ran through. If a tank starts to show this it is a manufactures defect when assembling the tank it is covered under the lifetime warranty for the tank makers to have in place. It can also be sought after for replacement since the tank makers are at fault for not assembling correctly. I have seen the tidal gardens video and am currently battling it myself on a 210 that i am refinishing. I have no idea who made the tank or i would be contacting them to replace. The thing is this hardly ever happens and when it does people dont know who actually manufactured the tank or what to do. Since this can take several years or multiple owners before it happens or appears in your actual tank. I would like to say that mistakes happen but not all the time in this case. Tempered glass is easy to tell iron side as the tempering mark will show what side the iron is on for example. If you can read the tempering mark the iron side is on the side with the etching. So you would assemble with the etching out. There is a lot of fail safes that can be done prior to putting a tank together if doing a diy. As well as when purchasing a tank. I know it can be exciting to buy and to just get it home and the process going but before buying the tank a thorough inspection should be done on any tank to avoid future issues or problems. The tidal gardens video is a good one but also put the fear into a lot of people that this happens a lot when it doesnt. Glass can also etch on the non iron side due to heavy dosing of nutrients and can permanently etch the glass it just is worse and happens faster on the alkali side of the glass.
Okay thank you for that tip I will do that
