Hiya,
If it were me i'd do this .............
Grab a razorblade algae cleaner set of razors, and some silicone remover (comes in tubes just like the silicone itself) and some aquarium silicone
Then i would find a home for fish etc for a few days, and of course keep the filter going to save the bacteria
Drain tank, 100% clean down the silicone that's leaking
Then tape/mask off the leaking silicone from top to bottom allowing 2" each side to allow you to remove the leaking silicone
Then use the razors and remover and get all that silicone off
Clean with some more silicone remover until it's nice base glass
Clean the cleaner off
Make sure it's real clean then remove tape/masking
Use a glass cleaner (google) and clean the area again
Mask off to size required to redo the join, then get to work with the silicone, but where the new stuff meets the bottom allow extra so it has a good bed to nit onto the old silicone (if that makes sense) asap silicone is done wait for a skin to form then peel away carefully the masking etc
If needed either use a corner silicone cleaner (like a plastic triangle tool) or use thumb/finger to smooth to match the opposite corner
Wait as long as silicone tube instructions say for curing
Redo filter/fish etc etc
That's how i'd do it ............
Cheats way, find exact leaking area, remove what you can and make sure its dry, clean clean clean, then apply silicone all over from top to bottom allowing the new stuff to overlap the remaining older stuff (done this years ago and never had a leak, gave tank away to a friend and as far as i know it never leaked)
Where does she stand, i guess under the 'not fit for purpose' law in the uk she stands in a very good position, a leaking aquarium after only 3yrs generally would come under 'not fit for purpose'
She should insist a repair like the above should be done for a start off
My guess price-wise for a do it for ya mom job would be £20, 6-10 quid for silicone then rest on razors cleaner etc
Only problem is doing the above scenarios is time/effort and fish moving
ATB
Tony
