Here is some stuff about nitrates, as many of us are familiar with the nitrogen cycle, but there are still some "behind the scenes" things.
Where Nitrates Come From
"The number one source of nitrates is feeding.
Most nitrates come from the proteins in uneaten fish food that metabolizes into ammonia. Fish that consume the food stop the decomposition to ammonia and break the cycle. In other words, fish excrement does not contain any nitrates. Fish will eliminate the nitrates for you, as long as everything you put in the tank gets eaten. Fish feces will decompose to ammonia, but the levels are far less intense than an equivalent weight of uneaten frozen fish food breaking down in the water.
I cringe when I see someone throw a frozen cube into an aquarium. The liquid from commercial frozen fish food cubes contains food particles too small for fish to eat. It just decomposes into nitrates. In fact, the packing juices contain more nitrogen compounds than the food itself. It is important to defrost and rinse frozen fish food through a net before feeding. If you have a persistent algae problem, this could be the answer.
Another source of nitrates is make up water. The US federal government allows up to 44 ppm of nitrates in drinking water from municipal sources. If you’re on a well, nitrate levels are not regulated at all. This could be a significant source of nitrates in your aquarium. Ask your water company for a free water analysis report. I don’t recommend testing your tap water yourself using your aquarium nitrate test kit because of the limitations in low level accuracy.
You don’t need a reverse-osmosis unit to remove nitrates, just a deionizing filter
. Products such as the Aquarium Pharmaceuticals Tap Water Purifier
works well. You can also purchase water from RO/DI machines found outside of major supermarkets and department stores. RO/DI water is the best defense you can have against nutrients, heavy metals, dissolved organics, and other compounds that wreak havoc in an established aquarium.
(My favorite part):
How to Get Rid Of Nitrates
Before we had high tech equipment and fancy chemical additives, most aquarists used water changes to dilute nitrates. For moderately stocked tanks, this is still the best defense to keep nitrates under control.
In addition, measuring nitrate levels is a great way to tell when a water change is due. Choose a goal of say 5 ppm. Test your tank regularly. When nitrates reach your goal, it’s time for a water change.
If your tank is heavily stocked with fish and/or corals, water changes alone may not be able to keep up with nitrate production. You will need to supplement water changes with some form of biological or chemical control. Here’s a list of common nitrate reduction methods that can help rid your tank of nitrates:
– This is the most inexpensive nitrate reactor on the market. It comes free when you buy a piece of live rock. The internal “nooks and crannies” harbor bacteria that are forced to live in anoxic (oxygen poor) conditions. The bacteria reduce nitrates to nitrogen gas.
(Which harmlessly escapes) The only drawback to live rock nitrate reduction is that the filtering capacity is very weak. Even with strong tank circulation, 50 pounds of live rock may be able to process only 2-3 ppm of nitrates daily.
– All algae, including macroalgae feed on nitrates. It is has been found that Caulerpa sp. Prefer to feed directly on ammonia. The good news is Caulerpa will prevent some of the ammonia in the tank from becoming nitrates. The bad news is that adding lots of Caulerpa won’t necessarily reduce existing nitrates. Still, any macroalgae in the tank will certainly help reduce nitrates and phosphates. Macroalgae also competes well against hair and film algae, minimizing its growth.
– A quality skimmer can remove ammonia, nitrites, and nitrates directly. The whole concept of the Berlin method is to combine live rock with a large aggressive skimmer as the only means of filtration. Such a setup is a powerful combination to combat the constant build up of nitrates. Many aquarists fail to get the Berlin Method to work for them, simply because they employ an entry level, poorly designed skimmer that does little more than aerate the water.
Deep Sand Bed – Deep sand beds make excellent nitrate reactors.
The way they work is that the deepest portions of the gravel do not receive replenished oxygenated water and become anoxic. This causes the bacteria to use a nitrogen molecule as an electron receptor instead of an oxygen molecule, and the result is the bacteria electrically transform the nitrate molecule (NO3) into nitrogen gas (N2). The gas is partially dissolved in seawater but then is quickly released into the atmosphere as it hits the water surface.
DSB’s are extremely efficient nitrate reactors and can handle very large loads, perhaps 5-10 times greater than live rock alone
. In-tank DSB’s have lost popularity due to misunderstood maintenance practices. Modern day DSB’s place the sand bed external to the display tank. These are typically DIY units made from deep containers (i.e., a Rubbermaid trash can) filled with sand and drilled with two bulkheads on opposite sides of the top of the container. Water passes over the top of the gravel bed just like an in-tank DSB. Nitrates permeate to the bottom of the gravel bed and are assimilated by anaerobes.
– There exists a continuing misconception in this hobby that bioballs are “nitrate factories”. The fact of the matter is that the same amount of decomposition occurs in your aquarium whether bioballs are present or not. The exact amount of nitrates are produced either way. The problem with bioballs is that nitrates are produced on the bioball surfaces, then they must find their way to the place where the denitrifiers live. In most setups this is the inside surface areas of live rock. When nitrate is produced in high concentrations on the surface of live rock, it is more likely to diffuse in situ to the deeper portions of the rock where in can be turned into nitrogen gas. Bioball-generated nitrates simply miss out on the opportunity to be converted because it can’t find the denitrators.
Other media with large surface areas such as Bio-wheels and even filter pads work the same way. It is important to replace mechanical filtering pads or filter bags frequently (at least once a month) to prevent them from becoming efficient biological filters. Even old activated carbon will harbor nitrifying bacteria once the carbon is exhausted and the pore structure becomes filled with organics.
To overcome these problems, people have tried different things to replace bio media. One alternative is to fill the wet/dry chamber with live rock rubble.
As long as it stays wet from the trickling water flow, the rock remains viable even though portions of it are out of water. But because live rock is a weak filter, you can never achieve the same filtering capacity as bioballs.
There are several new products on the market that overcome this. They provide areas for both nitrifying and denitrifying bacteria in the same media. The Cell Pore product
is made from ceramic that has been heated to a molten state and then heavily aerated as it cools, which turns it into a sort of “foam” rock. It contains thousands of holes and deep crevices- a similar structure to natural live rock."
I left some things out from the original article, but all in all I think this is a great extra to add to our knowledge of nitrogen. About the depth of the sand bed, I have heard that to house anaerobic bacteria it should be 2 or more inches deep and undisturbed. As to stirring it to release nitrogen gas, I am not sure...
I hope this helps anyone with "how do I remove nitrogen" questions!
P.S. The live rock thing only applies to saltwater aquariums.... Actually, this was written for saltwater aquariums, but the same concepts apply to freshwater, except for live rock.