WATER CONDITIONS AND
THE NITROGEN CYCLE
by John Kahl / GLCA's "Cichlid Evening Post" / April 2004
Water is water, right? It comes out of the tap in the kitchen and bathroom and, if it smells okay and doesn't taste bad, we usually don't give it a thought as we drink our eight glasses a day. Health gurus and doctors tell us to drink more water and we'll be healthier. So, we pretty much depend on our public officials and the people at the waterworks in our cities to make sure the water we drink and bathe in is of good quality.
Water chemistry for our home aquariums is a little more complicated than turning the tap and filling the tank. Water quality has serious effects on the health and happiness of our fish and, because of the various chemicals that arte added to protect us, we need to be very careful when we add fish to this water or this water to our existing tanks. If the water in their little corner of the world is correctly balanced, they will lead healthy active lives, and may even bless with fry from time to time. If they are forced to live in poor quality water, they may suffer and even die.
Although the water in your aquarium may look crystal clear and pure, it may not be of the highest quality due to many dissolved matters that can have an effect on your fish. Some of the invisible things that can be in your aquarium water are:
*Chloromine and chlorine from tap water ( These are disinfectants)
* Chemicals that cause the pH to be high (basic), low (acidic) or neutral.
*Dissolved carbonates and bicarbonates that stabilize the pH (buffers).
*Calcium and magnesium in dissolved forms that affect hardness.
*Organic materials.
*Ammonia.
*Nitrites.
*Nitrates.
*Parasites or bacteria that could be harmful to fish.
Everyone should have a basic understanding of the three important chemical properties of water. They are: pH, buffering capacity and hardness.
The first, pH, is used to describe the degree of acidity or alkalinity of any solution. Most fish are found in waters with a pH level somewhere between 6.0 and 8.0. Of course there are exceptions to this, as some cichlids prefer a pH as high as 8.8, but we, as home aquarists, are not usually concerned with the extremes.
It is important to fish health to maintain the pH at a fairly constant level. pH is sometimes confused with hardness, but as you will see, it is entirely different.
Buffering capacity is the total amount of buffers ( usually carbonates and bicarbonates), which are pH stabilizing compounds found in water. These prevent sudden changes in pH by absorbing excess acids or bases which may find their way into the water.
Hardness is the measure of the metallic ions in the water, usually calcium and magnesium. Hardness affects the fish's ability to maintain the balance between it's internal body fluids and the external environment.
Always remember, most fish can adapt to different water conditions if changes are made gradually, but different types of fish prefer certain conditions and some will not spawn or prosper if their water is not at least close to what their species prefers.
It is very important to initially test your tap water so you will know in advance if you have to make any adjustments so your fish will be healthy and happy. There are various natural and chemical means to adjust all the property of water so they will fit your species needs.
Now, we will look at the dreaded nitrogen cycle....everyone knows you should not feed your fish too much and you should always do your water changes and sip[hon your gravel regularly. Here's why.
Because your aquarium is a closed system, uneaten food and fish wastes will sink down into the gravel and begin to decay. This decay produces ammonia that is far and away the most detrimental chemical to your fish. In high concentrations, it leads to severe irritation of the skin and gills and can result in the eventual death of your fish. This is the first step in the nitrogen cycle and the first reason to do your weekly water changes and periodical gravel siphoning.
Two things determine the level of toxicity of the ammonia in your tank, pH and temperature. The higher the pH and the higher the temperature, the more toxic the ammonia becomes to your fish. An ammonia level that would be safe at 7.2 pH would cause stress at 8.0 and slow death at 8.4.
The second step in the cycle is when the friendly bacteria, known as nitrosomonas, start "eating" the ammonia and converting it to nitrites. These little guys do as much as they can and need to be there in sufficient numbers to handle all of the ammonia that the fish and uneaten food produce. They take time to develop ( usually 3 to 5 weeks) so it is important to use only a few expendable or very cheap fish when initially setting up an aquarium. The infamous "new tank syndrome" and it's eventual "ammonia spike" has struck down many expensive new fish over the years and probably has discouraged more prospective new aquarists from continuing in the hobby. Nitrites, which interfere with the fish's ability to use oxygen, are the second reason to do your weekly water changes.
A scary fact about nitrites is that they are pH dependent. That is to say that if the pH falls below 6.5, the nitrite will be converted to nitrous acid, which is very toxic to fish. If this happens, massive water changes (50% to 75%) are necessary for 4 to 8 days to alleviate the nitrous acid level.
The third step in the cycle is the conversion of nitrites to nitrates by another friendly bacteria called nitrobacter. They develop at the same time as the nitrosomonas and "eat" the nitrites, producing nitrates.
Nitrates are the least harmful of the three chemicals ( but can still pose a threat at high levels) and are actually helpful in aquatic plant growth. Regrettably, they are also used for growth by algae. Nitrates and the resulting algae "blooms" are the thrid reason to do your weekly water changes.
I use a homemade siphon that hooks up to my basement faucet and allows me to remove and replace 25% of the water in fourteen tanks in a little under an hour. If I am doing gravel siphoning, I add about 45 minutes to the total time. I figure it is a small price to pay to protect my fish from suffering and death.
So, now we know some of the basics of water chemistry and realize that we are the people at the waterworks who make sure the water is safe for our fish.