Watchdog has had several emails about a fish called river cobbler which is on sale at Asda and Tesco. It's also on sale at Sainsbury's where it's called basa. It comes from Vietnam and its proper name is pangasius.
Some of you looked it up on the internet because you'd never heard of it before, and came across all sorts of horror stories claiming it's fill of toxins, such as arsenic, toxic metals and harmful pesticides.
Lauren Antony from Lanarkshire emailed us to see if we could investigate this further and enlighten the nation, so we had a go.
Five tests
We sent a fish we bought in Asda to a lab, where the scientists did five tests to see if they could find some of the things the internet reports suggested they would.
The lab told us they couldn't find detectable levels of any of those substances - which to all intent and purposes mean they weren't there.
Now, as we only tested one fish, we can't say the scare stories are a load of cobblers - but we found no reason why anyone should worry.
The supermarkets say they've done plenty of their own research too, and maintain that they wouldn't sell any product that they weren't confident in anyway.
A fish called river cobbler
Some of you looked it up on the internet because you'd never heard of it before, and came across all sorts of horror stories claiming it's fill of toxins, such as arsenic, toxic metals and harmful pesticides.
Lauren Antony from Lanarkshire emailed us to see if we could investigate this further and enlighten the nation, so we had a go.
Five tests
We sent a fish we bought in Asda to a lab, where the scientists did five tests to see if they could find some of the things the internet reports suggested they would.
The lab told us they couldn't find detectable levels of any of those substances - which to all intent and purposes mean they weren't there.
Now, as we only tested one fish, we can't say the scare stories are a load of cobblers - but we found no reason why anyone should worry.
The supermarkets say they've done plenty of their own research too, and maintain that they wouldn't sell any product that they weren't confident in anyway.
A fish called river cobbler