Leaking filter tank - can it be patched?

Hi,

Long, long time since I've posted here.

We've had lots of tubing/pump and so on issues this summer.
The latest problem is what started as a pin sized leak in the filter tank.
Its still pretty tiny after about a week but it has gotten slightly bigger.
Its right along a seam in the tank.

Has anyone used anything to successfully patch a tank before? And if so, what did they use?

I did end up purchasing a used pump/filter set this summer so I could switch to the "new" used filter. But I bought 2 bags of sand for it as that's what the leaking one uses and now since looking at it closer I suspect it might take 3 bags. I can only get the sand in the city so hate the thought of another trip just for that (100 miles).

Any advice would be appreciated.

Also, sending positive thoughts Watermom's way.

Lori