How to Reduce Nitrate Level

I've got a 46 gallon freshwater tank that with a high Nitrate level. All other water stats are OK.

The tank is not over populated and uses a cannister filter.

What is the best way to reduce and keep reduced the Nitrate level?

Big water change, then detoxify with Prime.

more frequent water changes, plants...

Define high level. Also what is your pH? Very high NO3 in normally high pH can be OTS (old tank syndrome) which is mostly caused by organic debris in the substrate (and your canister filter). If your pH is normally low, then measure your buffer (kH), as OTS in low pH manifests itself as very low kH and a potential for pH crash (same root cause, substrate & filters).

Your best bet is to change the water more frequently, if the tank isn't overstocked 25% or so a week should take care of it.

If you don't like the sound of that, you could try adding plants, but they are a whole lot of work in themselves.

There's a nice little article about the nitrogen cycle here
http://www.shallowsea.com/article.html?select- article=4

You may find it of use.

As a rule though, you want more plants and more water changes.

I had trouble getting the nitrates down in my tanks as my tap water comes ready fertilized with 50ppm Nitrates, making it impossible to get below that level in the tanks. I recently started using a Nitra-King I bought from the LFS, basically a plastic tube full of nitrate removing resins, and my water changes are now having a real effect.

Check the level of nitrates in your tap water, especially if you are in an area of intensive farming.

50ppm nitrate in the tap water, that _would_ be a problem for most aquarists.

Plants, with CO2 and strong lighting, would be another option. Even one large sword in a tank of that size would make a measureable improvement. Anything that is a fast grower and not requiring very high light levels would be easy to start up. The OP could plant a few in pots so as to not have to mess with the existing gravel. Easier yet, get one of the many plants that will grow quickly as they float on the surface.

Depending on how often the canister is serviced, the OP may be able to improve the situation by a more frequent cleaning, or better yet, using a prefilter than can be rinsed weekly.

I am concerned about this too. Or I may be misinterpreting the statistics. It certainly wouldn't be the first time. My local water board published this;
http://www.3valleys.co.uk/pdf/quality_matters_2003.pdf

which lists their Prescribed Concentration Value of Nitrate in the tap water as 50 mg/l NO3, which I seem to remember as being the same as 50 ppm (but memory is a fickle thing). This is what I detect when I test the water straight from the tap.

Using the nitrate remover I have managed to get the water in the tank to around 20 mg/l NO3, which I hope will suit both plants and fish.

That 50 mg/l or 50 ppm is the limit for nitrate above which action will be taken to examine and possibly remedy the problem. Of 929 samples, your water board only found two with 50 ppm or more of nitrate.

If my tap tested 50 ppm nitrate with a test kit, I'd drink bottled.

If this water board can sell water with 49ppm NO3, you can be sure they wont spend the money required to purify it further.

I certainly don't drink the tap water.

If you have access to some reverse osmosis (RO)water you can use it to replace about half the water removed during a partial water change. The exclusive use of RO water will eventually remove most of the buffering chemicals needed to maintain a consistent pH. That doesn't explain the chemistry very well, but it may help solve your water problem. Live plants also use some nitrogen compounds, and several varities are easy to grow in an aquarium.