Sugru would be fine, but I asked upthread how big the project is. Sugru comes in small packaging so it's fine for a smallish bowl. It is inert, sets waterproof, and fine -40oC to +40oC.
Thank you @Dogmum, and @Pete8 for your replies, interesting thought, about aquarium shops. @Fire, sorry I have not replied to your question re size of 'bowl', truth be told, I have not really had time to look at it in too much detail. This item was actually given to me and is very heavy so I have not been able to properly turn it over and have a good look. I can say however, that at the moment I have noticed mainly hairline cracks, nothing too deep. I will look into sugru, thanks.
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