Keep a Water Change Routine

There is some controversy as to whether or not water changes are necessary in the hobby. To the author of this site it isn’t controversial at all, the answer to this question is yes, water changes are in fact very necessary in the hobby. The next question that must be addressed is why. To answer this question we must first understand the nitrogen cycle. Like you, fish must consume nutrients in order to live. Exactly like you there are things that they consume that their bodies can’t in fact use. Those molecules that their bodies can’t use is excreted out of their systems. This excrement becomes waste that begins breaking down in your tank and fouling the water.

In nature this excrement is broken down by decomposers that ingest these nutrients and further break them down until the excrement is so broken down that it recycles back into the system and either in an element or a compound form that is useful to other organisms. This forms a cycle where the atoms used are constantly transformed into biomass that is consumed, excreted, broken down and converted into mass again. This cycle is what is known as the nitrogen cycle. Now according to aquarium literature two bacterium are primarily responsible in the breaking down of these nutrients. Waste begins as ammonia which is highly toxic to aquatic life. Often times this is the first sign an aquarist notices when the water is fouling. Ammonia filled water is a very pungent, acrid smell that has been described as being sharp. In tanks ammonia can readily cause chemical burns in fish damaging the delicate structures of their gills and their bodies. Ammonia in the nitrogen cycle is treated by nitrosomonas bacteria and is converted to nitrite. Nitrite is also toxic to fish and aquatic life, luckily this molecule is also processed by Nitrospira bacterium into nitrate. In natural systems nitrate is incorporated into living plant tissues and anaerobic bacteria fix it into elemental diatomic nitrogen where it aerosolizes back into the atmosphere. Since aquariums do not have these anaerobic areas, we rely on water changes to remove excess nitrate. This is why water changes are necessary, it is these water changes that allow the elimination of excess nitrate in the system.

Now that we know why we must water change, is there anything else that we need to know? The answer to this is yes. In every municipality in the United States we use chemicals to cleanse the water of pathogens that have historically caused life threatening illnesses in people. In the United States two molecules are commonly employed to kill these pathogens that may exist in our water. In the United States we use chlorine and chloramine in order to kill water born pathogens. These chemicals represent a clear and present danger to aquatic life and can irrevocably damage and kill the fish in our aquariums. In order to change the water we must first neutralize these chemicals. The neutralization of these chemicals requires the use of an agent such as Seachem Prime. In the experience of this hobbyist you need to use 14 drops per a five gallon bucket of water. Keep in mind that even in this concentration this isn’t a magical process, it doesn’t instantly become safe. So it is recommended that you allow several hours to pass in order to allow the water conditioning agent such as Prime to diffuse through Brownian motion and convection throughout the bucket of water. Now how much should you remove? Generally speaking 10% of the entire volume of water is generally considered “safe.” However removal of up to 50% of the volume is commonly done by hobbyist without any ill effects observed in the fish. The general idea however is this, the more water that is exchanged, the more nitrates are eliminated from the tank and in general the healthier the fish will be.

It is also important to note that RO DI water is also a possibility in some house holds. Generally speaking these units allow for the direct use of water without treating it for chlorine and chloramine as both chemicals are eliminated by a properly maintained RO DI unit. If you have one of these units, it may still be necessary to further condition the water. In this case products such as Seachem Equilibrium is often used as it prevents pH crashes during the night time “dark reactions” in heavily planted tanks.

One final note on water changes. It is important to know what type of water you have and what type of fish you have when engaging in water changes. Simply put there are in general two types of fish. Most fish don’t really have water hardness requirements and most of the water used in the United States can also be used for these fish. The reason for this is simple, most fish lines available to the hobbyist are now so far from the wild varieties that they are no longer subject to the requirements of wild conditions that they originated from. They have essentially been through the generations and years in the hobby converted to the water conditions found locally. If you have these types of fish water hardness will not be as dire a problem for you to match. If however you have fish that come from super soft water and are closer to wild lines generationally, then you may have to further condition those fish to circumstances that more closely resemble the water of their home ranges in order to maintain their health and the viability of eggs/offspring.