thats hard to find any information on. Amazon sell a similar thing, but no mention of materials and nobody seems to have any idea what its made from. I did find one site selling something like it that was made from fibreglass, but not entirely sure if thats what that is?Sounds like it could be, but what be dubious without confirmation.
As a general rule (always be prepared for exceptions!) if it's food-safe, then it'll probably be fish-safe.Looking at the properties claimed for culinary applications, I can't imagine that it would cause problems in an aquarium. If it were me, mainly because my tankwater tends to be rather acidic, I would want to test it with both a conductivity meter (to see if it's leaching out any measurable ions at all) and with live critters (to see if it's leaching non-ionic organics that might be toxic to aquatic life ; I use Daphnia usually).If I happen to pass by a Poundland soonish, I'll pick some up and have an investigate. You're welcome to send me a bit if you want a quicker assessment ; though I really don't think there's that much of a risk if you were just to go ahead and use it for your intended purpose.
PM incoming!