APPLE VALLEY, Minn. - When you are looking through the glass at the sharks and fish at the Minnesota Zoo, you are only seeing a small part of this giant miniature ocean.

"About 75 percent of any aquatic exhibit that you see is out of view is behind the scenes. They are cold blooded, you have to have temperature control in your water. And also, they are swimming in their own waste. It's a sewer system and obviously you want to have a very good sewer system." said Allen Maguire, Curator, Life Support Systems.

To keep these two sharks healthy as well as all of the other creatures in this tank healthy the zoo uses three different types of filtration.

Mechanical, which removes the solid waste, Biological filtration using bacteria and finally Chemical Filtration.

"We will send it through a ozone reactor and that sterilizes the water before it returns back to the pool." said Wes Schmidt, Life Support Systems Operator.

For sea otters, who eat a full meal five times a day also create a lot of waste and sometimes the exhibit needs intensive cleaning.

"The whole exhibit, is completely drained and we spend hours power washing it to make sure we can get all of the debris and algae off." said Heather LaRock, Animal Trainer.

That can happen as often as once a month, most of the water that is drained can be filtered and reclaimed, but any wastewater goes directly into the cities sewer system.