First off, I know nothing about this compound other than what I've read so take this with a grain of salt. My guess is no one is going to be able to tell you definitively that this is safe. It does have a few things going for it in that it dissolves in water so you should be able to wash most of it out. It also apparently breaks down rapidly in the environment so it won't persist. Unfortunately they don't have a complete set of data on exposure
The Executive Summary here gives you the general idea and lists some other industries where this is used - http://www.who.int/ipcs/publications/cicad/en/cicad35.pdf
I'd probably keep looking but so far the indications are that you could use it if you were careful. Letting a tank like this sit for awhile, exposed to air before cleaning, wouldn't be a bad idea because of the short half-life of the chemical. Wash it out several times if you decide to use this tank. You might also let water stand in the tank in case any has leached into the walls of the tank.
Hope this helps