My tank (that im setting up) is 2nd hand, and as I was about to put water into it (outside the house) to see if there are any leaks, I noticed there is some mold and whitening between the glass joins in the edges of the tank.

How serious is this for weakening of the tank? Assuming the mold is in there, that seems to me that the silicone cant be joined together properly at these points (ie there is nothing gluing the glass together at these points) , is that true? At one point there is about a 10cm length where the whitening goes almost right to the far edge of the glass (perhaps meaning that there would not be much left holding that together???)

Im trying to add a photo but whenever i upload it, i get a red circle with an exclamation mark (like an error). Its only about 500x600 pixels and 90KB in size, i dont know what the size limit is but thats pretty small

There is also a chip in the edges , the seller said that had been there for years and never leaked.