Brackish water takes in quite a variety of water conditions. Brackish water is simply water with a less concentrated level of salt than sea water and more than fresh water. The growth of the plant will depend on the level of salt in the water, for sure. If you're talking about up to a tablespoon or less in every five gallons of water, the plant should be fine. Bamboo is a very slow grower. If you want a faster growing plant, then research the Agloanema or Chinese evergreen.
"Fear not, my young apprentice. Just change the tank water."