A TINY fish tank that doubles as a music speaker has sparked outrage among animal activists and aquarists.
The iPond - up to 15 times smaller than the recommended tank size for the fish it contains - is proving a hit with Christmas shoppers.
One Sydney store has sold out of the $70 device and other outlets are reporting brisk sales.
But the RSPCA has called on the device to be banned because it is too small to provide fish with adequate oxygen supplies and a clean environment.
The iPond is sold nationally by the Pets Paradise and Pet Goods Direct chains. Users can play their iPods through a speaker built into the bottom of the brick-shaped tank.
The tank's water capacity is about 650millilitres once rocks are placed in it.
Pets Paradise is selling Siamese fighting fish with the iPond.
The fighting fish are native to South-East Asia and have a "labyrinth lung" that allows them to take in oxygen from air. Typically they live in puddles and rice paddies.
A Melbourne Aquarium spokesman said Siamese fighting fish required a minimum tank size of 10 litres - dramatically more than the iPond provides.
Animal Liberation Victoria's Noah Mark said he was disgusted by the invention.
Studies proved fish had memories well beyond a few seconds and were social creatures that experienced pain and boredom, he said.
"The fish in this thing does not look like it has very long to live and it can barely move," he said.
"Even if it does live it's not [a] life worth living ... it's really just a torture box."
Acoustics expert Jason Gedamke said there was no doubt noise from the speaker would escape into the water.
"The speaker is directly coupled to the outside of the tank ... [so] you are going to have a small level of sound introduced," Mr Gedamke said.
"It's the same as putting a fish tank on a speaker."