Carbon does get rid of some nitrates, however if there are fish in the tank, the process will take too long, and the longer they are exposed to it, the longer they will suffer from toxic the material. It is advisable to perform a large water change by preparing the replacement water from an RO system, brought up to temperature. If this is not at all remotely possible, you can use detoxifiers like Amquel to comfort the fish a bit, but you will still need to change that water soon, and repeatedly until the nitrogen bacteria cycle completes or all medication is out of the water column when the treatment is over and nitrogen cycle can proceed once again.