Of all the underwater creatures you can find in aquariums, a goldfish might not seem too special. But there’s one goldfish in Shima Marineland in Japan’s Mie Prefecture with a life-story more exciting than most.

Thrown into a tank as food for a larger species, this plucky fish not only escaped predators, but managed to slip into a water filtration tank where it survived undetected for seven years – growing to a length of 25cm (10 inches) – before being discovered by aquarium staff.

Back in April, a member of staff was cleaning a water purification tank when he thought he saw the shadow of a large fish. The 3 metre by 5 metre (10ft x 16ft) filtration tank, located underneath the exhibition tank, should not have any fish in it at all – so after using a net and a flashlight to scout around, he was surprised to discover this huge goldfish was living in there!


The fish in the exhibition tank are flesh-eating arapaima, one of the largest freshwater fish in the world. According to aquarium director Tomoyuki Satonaka, the aquarium’s arapaima used to be fed live fish – but the practice was stopped seven years ago when the aquarium began feeding the fish more conventional solid fish food.

The tiny goldfish escaped through a 1cm diameter pipe into the filtration system, where it lived on scraps of leftover food pumped out of the main tank. The goldfish’s environment over the last seven or so years appears to have been rather pleasant – the bottom of the large filtration tank was coated with sand, and the leftover food constantly washing through from the arapaima’s tank provided a perfectly balanced diet for the brave little fish.

▼ Arapaima can grow to over 4 metres (13 feet) long, so it’s perhaps no surprise that our little goldfish didn’t fancy ending up as dinner.

2892681356_18b893b79d_oCliff/nostri-imago on Flickr

In a large enough tank, goldfish can grow up to around 30cm in length – and this little guy had plenty of room. Aquarium staff say the fish is in excellent condition, with no damage at all to its eyes, mouth or fins. The only sign of its unusual living conditions is its colour – because the tank it was hiding in was unlit, the fish is a pale yellow colour rather than gold. This pale colour may have been what helped it to evade detection in the tank for so long. Despite staff cleaning the basin once a month, they had no idea there was a monster goldfish inside.

And this adventurous fish’s luck hasn’t run out yet, either – it’s now the star attraction of a special exhibition at Shima Marineland, where visitors can learn all about goldfish, as well as the story of this one brave little creature.

Sources: Yahoo JP, Ise Shima Keizai Shimbun, Shima Marineland
Featured image: Shima Marineland Facebook