nitrogencycle

The Nitrogen Cycle

The nitrogen cycle is the process that keeps the water in your pond healthy and safe for your fish. Simply put, it is the oxidization of ammonia to nitrite to nitrate by bacteria. Until fish are put into a body of water, it' s fairly sterile. Once the fish go in, the cycle starts. This cycle can take anywhere from 8 to 12 weeks to complete depending on the water temperature, pH and KH levels. Fish loads starting out should be kept low and feeding to a minimum.
     The fish give off ammonia, NH3, from respiration, about 75%, and from the decay of waste products. Decaying organic matter such as, uneaten food, leaves or dead fish also contribute to ammonia levels. Ammonia levels will start showing up a week to ten days after the fish are introduced and will continue to rise for several more weeks. While this ammonia is building up, bacteria, Nitrosomonas, are also developing. This bacteria oxidizes, eats, the ammonia turning it into Nitrite. Once there are sufficient numbers of the bacteria, the levels should fall to zero. This will take 4 to 6 weeks. Ammonia is quite toxic, especially at higher pH levels, greater than 7.5, so care should be taken to maintain pH levels in the lower ranges. Thsi will keep the NH3 in the form of NH4, ammonium. Ammonia should be tested for and the fish protected from it, using a chemical binder such as Amquel, Ammo Lock 2 or other similar products. Fish that are showing signs of high levels will be sitting on the bottom, gasping, display red streaks in their fins or body, dropping their slime coat and just generally stressed out. Water changes may help if the levels are extremely high.
       The result of the ammonia being oxidized is Nitrite, NO2. At this time a second type of bacteria starts to develop called Nitrospira. This bacterium oxidizes the nitrite into nitrate. It was long held that bacteria called Nitrobacter did this conversion but recent research by Dr. Timothy Hovanec has shown this to be wrong, for fresh water. It can take anywhere from 6 to 12 weeks for nitrite levels to peak and then fall to zero. This can be a very stressful time for the fish as the ammonia levels are also rising. Higher temperatures and pH levels will help the Nitrospira to develop quicker, but pH levels should not be raised until the ammonia level has started to drop though. This again is a highly toxic chemical for the fish. It can impede the fish's ability to breathe...Brown Blood Disease.The fish can be protected from high nitrite levels by using salt, at a rate of 1 lb. per 100 gallons. Any salt can be used for a pond or an aquarium but should be free if anti-caking agents like YPS, yellow prussiate of soda.

        The last chemical produced is Nitrate, NO3. This chemical is not generally toxic to the fish but levels should be kept below 50ppm. This can be accomplished using water changes, floating plants or Trickle Towers. A ''TT'', is a container that's filled with a large surface area bio media. The water is then allowed to trickle down over the media. The result is that the nitrate is gassed off in the high 02 environment. No one is quite sure why this happens or how it happens, but it does work.
       After 8 to 12 weeks, sometimes longer, both ammonia and nitrite levels should be at zero, if they are not then something is wrong. Either the fish load is too heavy for the bio filter size, the flow through the filter is too slow, too much uneaten food laying around, etc. At that point you should start cleaning, increasing or changing things till you find out what's wrong.
        These bacteria grow on every surface within the pond and the filter, including the fish, but they need somewhere to colonize in large numbers. This is where the bio filter comes in. There are quite a few different bio media on the market, from PVC shavings or ribbons, beads, porous mats to plastic scouring pads. Whichever one is used there should be a lot of it. All filters should have a section dedicated to the bacteria and this section should not be disturbed unless absolutely necessary. These bacteria can be knocked off or washed off with very little effort. If the bio media has to be washed off, then pond water should be used. Do not use a hose or chlorinated water, as this will destroy them.
       These bacteria grow their best when they have higher pH and KH levels and lots of oxygen. A pH of 7.8 or greater and a KH of 80ppm or greater will help them along just fine.
       There are a lot of products on the market that claim to have live bacteria in them to speed this cycle up, but most of them do nothing. They may help the bacteria that are developing by supplying them with minerals and extra nutrients but that would be all.
       When the temperatures start to drop in the fall, the bacteria will slow down to the point where they are doing nothing. Below 55* they are dead, dying or dormant. There is great discussion and disagreement as to which it is. One way or the other they are not doing anything.