site logo

Main Index > Step by step start up > Nitrogen Cycle
1 visitors online


Nitrogen Cycle

Introduction: First of all What the heck is this and why would you care? Well, this cycle is the mistake of all newbies to the hobby and why most people fail in their attempts at keeping fish! This cycle is the natural way food, fish waste, and fish breathing is broken down in the aquarium. After the tank is setup and you put those little fishes in the tank the cycle starts. Yes, that is right the cycle starts the second the fish are dropped in the tank! The first thing that happens is the fish breathing. Through breathing the fish enter into the tank along with Carbon Dioxide and other gases is Ammonia. This Ammonia is the first step in the cycle. This Ammonia is broken down into Nitrite and later on the Nitrite is broken down into Nitrate. This Nitrate is the final stage in the cycle and is the easiest element to keep in check and the least toxic to the fish in the tank. These elements must be closely monitored and kept in check. Through biological filtration these elements can be kept at minimums. Biological filtration is very important in any aquarium. These filters are, undergravel filters, ceramic pipe and sponges in canister filters, Bio Wheels on back box filters, and others which we will go into more depth in other pages. These filters are where helpful bacteria can attach themselves and grow to remove these different chemicals and make your tank healthy for your fish. Where most people fail being new to the hobby is not understanding this cycle. Me being one of them and having your tank become a glass coffin. Food broken down in the tank also adds to the ammonia levels and is one of the leading causes to fish deaths in a new tank by newbies. Over feeding fish is a major no-no! Especially in an unestablished new tank. And the smaller the tank the worse off it is. Small amounts of water are very unforgiving. For this reason when starting a new tank feed your fish very little!!! The fish will survive on very little food with no problems but by over feeding and sending ammonia level off the charts they will surely visit fishy heaven. Well lets get into each part of the cycle.

cycle graph


First cycle (Ammonia): NH3 and NH4. The first part of the cycle starts with ammonia. And also this is the most toxic substance to fish. Ammonia is given off by fish through their gills. Also through fish waste (Poop and pee). And other sources such as a dead fish left in the tank and food decay. A test kit to monitor this is a must. Levels in a new tank will soar and should be monitored daily and always keep an eye on the fish. This first cycle is the toughest and should be toughed out by fish that can tolerate these levels better than expensive low tolerant fish. More on the best fish to use later. If done properly this cycle can be dealt with and no problems will arise. Lucky for us that there are bacteria in the air everywhere that thrives on ammonia. When enough ammonia is in the tank these little hungry bacteria settle in the tank and start eating the ammonia. Now this might not sound like a tasty treat for you or me but these bacteria love the stuff. They will establish a colony in a tank in the gravel, clay pipe, Bio Wheels, ECT. Anything that they can attach themselves to and multiply on. Unfortunately the ammonia levels soar during this time before the bacteria can establish itself and keep levels low. With just .5 to 1 PPM (Parts per million) fish will show signs of stress clamping of fins and fast breathing through their gills. At higher levels these signs get worse and more noticeable. With levels of 6 to 7 PPM fish deaths could occur. In a new tank these and higher levels will be reached before the ammonia-eating bacteria can establish itself and drop levels. With pH levels above 7 (neutral) or alkaline water this ammonia is even more toxic to the fish. Acid water with ammonia in it is less harmful to fish than is alkaline water. Water changes at this time are a MUST! You must change the water at the very least by at least 25%. More preferably the water should be changed every 2 or 3 days. Get a gravel cleaner and clean the gravel every week at this time. You do not want anything increasing the ammonia level any higher than they have to be. Make sure the tank is well aerated during this first stage as well. Why your fish are breathing heavy is because the fish are being suffocated by the ammonia. Ammonia interferes with the fishes ability to get oxygen into their bodies. It may sound dumb but the fish drowns from lack of oxygen. High aeration, low feeding amounts; small number of fish, and frequent water changes and cleanings at this time and you and your fish should make it through this phase.

test kit

Second Cycle (Nitrite): NO2. Nitrite is the waste product from the ammonia-eating bacteria. This substance is less toxic than ammonia but in high levels it to can cause death. Nitrite in a fishes blood stream can hamper their red blood cells in their ability to carry oxygen. At high levels this to will cause fish to suffocate and can be seen by a fish swimming frequently to the surface to get air. Although I have found that the first stage is the most difficult for the fish and once this stage has been cleared and the fish survive this stage should be easy. Nitrite eating bacteria will establish itself to in the gravel and other media as does the ammonia bacteria. Although the same as with the ammonia bacteria. Nitrite levels will soar as it takes time for the nitrite-eating bacteria to establish its colony. You should get a test kit for this as well. For when the nitrite levels hit zero your tank will be fully cycled. Also I noticed that this is the slowest and levels soar the highest during this cycle. All of my tanks stayed off the readable chart levels for more than 2 to 3 weeks. And even then only slowly dropped to zero. Nitrite eating bacteria take longer in their multiplying time. And since the nitrite level are rising quickly from a pretty well established ammonia eating bacteria it takes a while for the NO2 eating bacteria to equal the output from the NH4 bacteria. Be patient at this stage and you be on your way to being able to add new fish.

Respiratory cycle
photo from Rolf C Hagen Inc.

Third Cycle(Nitrate): NO3 Once you have fully cycled your tank the NO2 bacteria will produce NO3 nitrate as a waste product. This is a pretty stable substance and is pretty much nontoxic. But at high levels this to is toxic to fish. This is where your plants and water changes come in at. How it was told to me was "as to not pollute change the water and dilute". Nitrate is a natural fertilizer Plants will use the nitrate as a food source. Also if you do not have plants in your tank save the water for houseplants. The fish waste and the nitrate will combine for a nice food source for them as well. They will also like the water with no chlorine in it. Nitrate at levels of 80-140 PPM. Can also be toxic to fish so be sure that you do water changes at least every two weeks. For those of you that have 10 gallon tanks a once a week no less than 25% water change should be done. At lower water volumes and no plants levels climb quickly. My 10-gallon tanks will be from a 10-20 PPM. To 80-100 PPM. in one week at around 30-40% water changes. I change the water every week. There are bacteria that will eat nitrate and require another filter that contains sponge balls to attach themselves to. I believe they turn the nitrate into nitrogen gas and it leaves the tank but water changes are less expensive and the fresh new water will be good for the fish.


Conclusion: I will share with you my results of dates and times and what tests I performed. I did not have the help of using someone's gravel or other material to speed the process along. If you know of someone or if you know of a pet store that takes good care of their aquariums. Ask them for some of the gravel. At the pet store ask if they will give you a scoop of gravel or if you have to purchase a scoop of it. Remember that the gravel they give you should be place into a piece of cheese clothe and place in you tank after the fish have been in there for 3 to four days. This will make sure that some ammonia levels have been raised to a point where the bacteria have a food source. You can place the gravel right in the tank if you wish and the gravel matches or does not bother you with your own. This will jump start your tank and shorten the time it takes to cycle the tank. Remember to be patient and don't run out and Max that tank out without cycling it. The ammonia levels will jump of the charts and you will lose your fish. Watch the over feeding of the fish. A hungry fish will last longer than a fish that cannot get oxygen into its body. Aeration at high levels makes that water extremely oxygen rich. Change the water often. Changing the water often will dilute levels. After the tank is cycled then you can add more fish. Fish should be added at a slow level even after the tank is cycled. Remember that the amount of bacteria in the tank will only rise to a level of waste being produced by that number of fish. Adding a lot of fish will again rise levels of ammonia and nitrite till the bacteria can raise it's levels to match the new load in the tank. Add fish at 4- 6 fish per 1 to 2 weeks as to number 1: raise levels slowly and number 2: not shock the community with large numbers of new fish. Next we will talk about types of fish to use for this cycling of the tank! Stay tuned! Same Bat (I mean BAD) channel!





Privacy Policy | Contact Badman's Tropical Fish
Copyright © 1997-2009
All rights reserved. Reproduction of any portion of this website's content is forbidden without written permission.