I am currently using Fluval Lab Grade Nitrate Remover (ion exchange resin) in a canister filter on my 125 fresh tank and it is doing a great job.
My well water is 35ppm nitrates, so water changes are not helping me there. Within 5 days of using this product, my tank water was reduced to less than 5ppm.
It works by exchanging Nitrate ions with Chloride ions. Once it has exchanged all the ions it can, you remove it and recharge it, which can be done 4 to 5 times before it loses its effectiveness. I recharge it about once a month.
To recharge it, you soak it in salt water (sodium chloride) for 24 hours to replenish the chloride ions.
If you are doing water changes to reduce nitrates, using this product will take the place of that. Just make sure you have a good nitrate test kit.
Another alternative to water changes for nitrate removal is an algae scrubber.
Hope this helps.