Hello; I agree with monkeybite. My first guess is the three points are stress points. The outside frame should not necessarily mean the glass is compromised. I started out with metal framed tanks back in the day. The iron frames eventually rusted away but be that time silicone was available. I ran a small tank with no frame at all for a long time.
The thing is you have recently picked up a used tank and it is showing some possible problems. Should you worry? Yeah some anyway. 220 gallons is a lot of water to get out. Not sure exactly what you should do.
Were it mine I would at least try to check the stand for true but that means taking the tank off.
By the way when you set up the stand and tank, did you shim the stand at the floor? Hardly any floor is level and true. I always shim and true my stand at the floor before placing a tank on top.
Hello; By pin hole do you mean an actual hole or small flaw in the glass. A flaw is a flaw but it may never fail, then again... Some depends on where it is. AT the bottom of the tank the water pressure is highest. Near the top the pressure is less.
