Purchasing a freshwater master kit may be the most useful, money saving item you invest in as a aquarist. Any good test kit will include a way to test pH, ammonia, nitrite, and nitrate which will allow you to catch any major issues before your fish can be harmed. If you are new to the hobby, it may be hard to understand the importance of this kit or more importantly how to fix any problems that are revealed by it. My personal favorite kit is the API Freshwater Master Test Kit because it includes all of the tests I listed above (plus high pH) in a single convenient package. Some people like to use test strips, but these can be less reliable since each time you open the container the humidity in the surrounding room enters and may alter the results by the time you use the strips.
The most important cycle that occurs in your aquarium is the nitrogen cycle which begins with ammonia. Ammonia is very toxic to your fish and is fatal even in low concentrations. On a daily basis ammonia is created as a result of your fish eating then excreting waste into the water. This level of ammonia is manageable if you have enough beneficial bacteria in your aquarium to process it all into the end product of nitrate, which is much less harmful. If however the ammonia in your aquarium suddenly spikes from either an excess of food breaking down or a recently deceased fish inside the tank, the bacteria may not be able to process it fast enough to keep your fish safe.
Your goal as a hobbyist is to keep the concentration of ammonia at 0 ppm (parts per million). Hardier fish are able to handle slightly higher concentrations than others, and I’ve even seen some handle a concentration as high as 1 ppm with relative ease but any higher and your fish can begin to sustain long term harm.
Short Term: If you test the ammonia concentration and find it may be high enough to harm your fish, a short term solution may be necessary. Prime and AmQuel do a good job of detoxifying ammonia for roughly 24 hours and if you add a standard dose to your aquarium you may be able to prevent harm to your fish. The ammonia is temporarily converted into a safer chemical for just one day, but this chemical can still be processed by your bacteria during that time which will help to reduce the concentration levels. After those 24 hours if the levels are still too high you can add another dose, but keep in mind that with the addition of too much AmQuel or Prime the water’s pH may begin to drop.
Water changes are also a method to reduce the ammonia concentration within your water by removing the contaminated water and replacing it with clean, ammonia free water. Even though you are helping your fish, you don’t want to do too large of a water change as extreme changes always stress out fish and may end up being fatal. Instead, just do a 25% change (or in more extreme cases, 50%) once a day until the levels are safe again.
Long Term: There are two important things you can do to stop this issue from happening again. First, find a way to seed additional bacteria within your aquarium by taking a filter from a well established tank and shaking it around inside the aquarium. Second, find the source of the ammonia spike. As mentioned previously, overfeeding food or the death of a fish add large quantities of ammonia to your aquarium so take a look around. Is there food rotting on the bottom? Are all your fish accounted for? Sometimes we get into autopilot and don’t notice these things happen. Another problem that I commonly see is that an ammonia spike may occur if you rinse your filter media off in untreated water. The chlorine in this water may have killed all the beneficial bacteria on your media essentially restarting your tank. If this is the case, you will want to keep feeding to a minimum and perform more frequent water changes while your bacteria recolonizes your aquarium.
Nitrite is the second step in the nitrogen cycle and although it is much safer for your fish you still want to keep the concentration as low as possible. Typically I only test for nitrite when establishing an aquarium and high concentrations of it may indicate your aquarium is not fully cycled or you may be overfeeding your fish.
If your nitrite is high, you are likely still cycling your aquarium and if you have no fish then there is little cause for concern. If, however, you do have fish already you may want to move them to another aquarium or do a partial water change in order to reduce the concentration levels. As with any water change, doing partial changes over a longer period of time is the safest way to ensure the fish are not stressed out by sudden changes in water chemistry. So perform a change up to only 25% unless the concentration is extremely high, in which case a 50% change may be necessary.
The end product of the nitrogen cycle is nitrate, which most (but not all) fish are able to handle up to a concentration of around 20 ppm. Again, as with the other chemicals involved in the nitrogen cycle, the goal is to keep the nitrate concentration as low as possible as not every fish can handle high levels of nitrate. Typically nitrate levels will begin at 0 and build up over time which is the reason we perform water changes in the first place. Water changes allow us to remove a portion of the nitrate in our aquarium and dilute it with fresh water from our tap (remembering to treat this water with a dechlorinator before subjecting fish to it). One side effect of nitrate is a growth in unwanted algae which loves to grow on the glass and other surfaces available.
Water changes are the fastest way to remove nitrate from our aquarium and that is the primary reason we replace at least 50% of our water every month. Performing smaller changes more frequently is the best way to keep nitrate down and not stress out your fish. Additionally, nitrogen is one of the three primary components of fertilizer and as such plants will readily consume it. This means that in addition to making the aquarium look better plants also help us maintain nitrate levels in our aquarium.
The pH of your water, aside from the temperature, may be the most important component in terms of water chemistry. PH is an indicator of how alkaline or acidic your water is, with neutral water resting at 7.0 on the scale. At 7.0 most freshwater fish will do well within your aquarium, but this varies based on species. Most fish thrive when the pH rests between 6.0 to 8.2. A majority of the water straight out of the tap in the U.S. tends to fall a little high on the scale, but as the water in your aquarium begins to “age” the pH will begin to fall. That is the result of an acid being created as a byproduct of the nitrogen cycle.
Although you do want to keep the pH of your aquarium within an acceptable and stable range, you typically don’t need to worry too much about changing this parameter. Let me explain. As I said the typical pH of water in the U.S. is on the higher end, but as time goes on the nitrogen cycle will begin to lower it. Obviously you don’t want to let the pH drop too low, but typically before this occurs you will perform a water change, which will naturally raise the pH of your water once again. If however you are the opposite and have a low pH there are ways to raise the pH at an acceptable and effective rate. Many companies produce a freshwater buffer which effectively raises the pH up to approximately a 7.0 and keeps it there until its buffering capacity is completely used.
Although it was mentioned several times, I just want to reiterate the importance of providing your fish with a stable system both physically and chemically. Taking steps which cause a rapid change in pH, nitrate, or any of these other parameters causes undue stress on your fish which may result in them contracting ich or another disease. You see, fish can typically handle one parameter being off with relative ease, it’s when multiple things go wrong that their ability to continue may be compromised.
I also want to point out that most problems in an aquarium are caused by one of the parameters listed above being off. If a larger number of hobbyists were to test these parameters I believe 90% or more of the problems I commonly see would be eliminated. That is of course keeping in mind the temperature of the water as that is the other essential parameter I do not cover here.