Bamboo, tropical or temperate, will put up shoots that grow to full height in a few weeks. After the culms reach their full height, they never grow any taller or larger in diameter. While some bamboo do send up shoots more than once a year, you will not have any luck finding a bamboo that does this continuously.

For your purposes I would choose another plant. Do you have a controlled environment that would allow you to continuously grow something simple...like lawn grass or moss?

Can you explain what you mean by "constant year round growth"?

Basically I'm setting up a system to remove excess nutrients(nitrate, phosphate), that are harmful to fish, from aquarium water. So I need something that will constantly be using these nutrients. The faster the plant grows the faster it will remove nutrients from the water.

The plant will either be grown in a hydroponics style flood and drain system or emersed in water.

I thought of using mangroves, but I was hoping to find something that would grow faster.

So the plant will be growing in water? If so, bamboo is not the right choice. Have you Googled "aquaponics"?

bamboo grows constantly as long as temps stay above 40 deg. F. Spring and Summer it grows above ground and fall and winter it grows below ground. It's a voracious feeder that you would be hard pressed to provide enough aquarium water for.