Used 20g tank - how to determine if joint seals are good

[StepanLevin]

I'm new to the hobby so just a brief intro:
I have an Aqueon 10g starter tank I use to support a fantail goldfish a friend of a friend could no longer care for. In addition to the standard HoB filter I've added a DIY container filter for additional biological and mechanical filtration. Based on recent water tests it seems like the habitat has cycled and there are no glaring concerns.

I recently received a used 20g for free. I know it was manufactured in 1991 and has likely been resealed at least once. The previous owner advised that I reseal it as it had not been used since their "mom had passed". I take this to mean that it has been sitting dry for at least a year if not longer.

I have attempted to reseal the tank and am currently water testing it. It has been full for roughly 12-18hrs with no signs of leaking, I intend to leave it full for at least 48hrs.

My concern is with the condition of the joint seals as they appear with the tank full and whether there is a way to visibily determine if they are no good. Here are some images for reference:

Here is a link to more images if they are would be helpful:https://imgur.com/a/MSJs7Ut

 

[Ulrichsd]

You can kinds of see a little separatation evident by the air in the seams. A 20 g is relatively small so not a lot of pressure. If it holds water you are probably okay, just don't try to move the tank with water in it. If it does end up leaking you can get 20 tanks relatively cheap.

 

[Brookster123]

can you leak test it for a week outdoors or somewhere that can take water spills? If you have an extra $20 bucks of just buy new. It's literally the worst thing in this hobby when you spend a weekend setting up and scaping a tank just to have it fail soon after... been there a couple times and it sucks.

 

[StepanLevin]

Unfortunately I don't have an area where I can safely perform a weeklong outdoor test. I appreciate your input and advice, based on it I think I will set this aside to either be redone entirely, repurposed as a terrarium or given away. Thanks!