Getting solder to stick to aluminum can be a real challenge.
I tried this stuff on a tank once but it didn’t work.

Home depot has the aluminum brazing rod and would be a
good choice here but there is learning curve with this stuff.
It you try this, fail, and then take it to have it welded you’ll
need to get it or anything you try off first.

Do you have a tank to practice?
You would probably need to drill the
hole out to remove any contaminants.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.