This is just my personal experience, im sure others will dissagree.
Some people will tell you to try to make places for anerobic bacteria to live in the sand or rock. They are aiming for some N2 liberation through bacterial means. I personally dont think this is a good thing at all. If we were only adding nitrogenious compounds into the tank, then I might be a fan of this method, as it would compleate a cycle.
The reality is though, we definately arent just adding nitrogen compounds into the tank when we feed. If you use cheatomorphoria algae for your ONLY means of nutrient export, you have a way of storeing not only nitrogen compounds, then you have an ability to rapidly remove all of the compounds you are adding to the tank when you feed.
If you just wana kill off the nitrate, run a couple of 30ft legnths of 3/16" coils of black plastic tubeing siphoning from the upper tank to the sump. Place the tank side of the tubeing down low in the tank to try to prevent bubbles from entering it as best as possible.
After you have the tubes siphoning to the sump, hit the sand bed with a gravel vac or wipe down the insides of the filters (not required by starts the process much sooner) or other nh3/4 to no2 bacteria holding places.
This will cause bacteria to rapidly find its nitch inside the coils of tubeing. This filter can not break down nitrates unless the upper portion of the tube has areobic bacteria in it to use the O2 in the water as it produces nitrate. The nitrate is produced in the upper portion of the tube, while leaving the lower portion of the tube anerobic for converting the nitrate it created into nitrogen gas.
Just a couple of coils of tubeing at about $3 apeice (must be opaque tubeing so algae wont grow), Will rapidly drop nitrate level down from anything to about 5-10ppm. However, its no better than useing rock or a sand bed, so I would highly recomend going the cheato route.
