Even though you can’t see or smell nitrate, the impact of this chemical can be deadly to aquarium fish and aquatic plants. Every aquarium owner will encounter nitrate issues at some point, but keeping on top of nitrate levels is fairly straightforward. In fact, even a complete novice can keep nitrate levels in check and quickly work to lower them should levels become dangerously high. Below, we break down all you need to know about nitrate, how to measure it and how to bring down levels in your aquarium when required.
Nitrate Explained
The main cause of nitrate levels in fish tanks is ammonia. This chemical occurs naturally and is often produced when faecal matter and food waste dissolves in aquarium. If you’re growing aquatic plants in your aquarium, these can also be a source of excess ammonia levels. At high levels, ammonia and nitrite are both incredibly harmful to fish species. However, nitrate is less dangerous in moderate doses. However, once nitrate levels build up to a high enough level, you will quickly start to see a detrimental impact on the health of your fish stocks.
The real danger of nitrate is that it is a silent killer. Unlike other chemicals, nitrate has no discernible odour and cannot be seen by the naked eye. Unless you’re testing your aquarium water regularly to keep an eye on levels, nitrate concentrations can become dangerously high without you realising it. In fact, many aquarium owners don’t realise they have a nitrate issue until the water within their tank becomes tinted with green. This green water is in fact an algae bloom. Algae thrives in water with high nitrate levels, although many varieties can multiply at lower levels.
How to Measure Nitrate Levels
The first step you should take to rectifying nitrate issues is to measure nitrate levels in your aquarium water. You can pick up water testing kits inexpensive from online retailers and most pet shops. Water testing kits are incredibly easy to use, with a detailed colour chart included that will give you a clear idea of the nitrate levels you are dealing with. There’s no strict rule on acceptable nitrate levels. Some fish species thrive at higher levels, although such tank conditions are hard to maintain unless you have been keeping fish for years and have considerable experience.
If you’re maintaining a freshwater tank, you should aim for nitrate levels within the 5-10 parts per metre range. Anything above 20 ppm is simply too high. Readings of freshwater aquariums will usually yield higher nitrate levels than saltwater tanks, but this is to be expected. In fact, if you’re keeping a marine tank with reef substrates, you want to be aiming for as low a nitrate level as possible.
Unless you’re testing aquarium water regularly, there’s no clear indicator that the nitrate levels within are dangerously high. Most fish species will not show any obvious signs of nitrate poisoning until nitrate levels skyrocket beyond the 100 ppm range. Excessive exposure to high levels of nitrate is catastrophic to fish health. Even if the nitrate doesn’t eventually kill them outright, the toxic stress can make them more prone to disease, stunt growth and reduce fertility. Once fish have been exposed to high levels of nitrate for long enough, the damage becomes more obvious.
Their routines will ultimately become affected, with lethargic swimming behaviour a typical symptom. This may affect their appetite and reduce feeding behaviour, leading to malnutrition and eventual starvation. Some fish may also exhibit physical symptoms, such as discolouration or unsightly sores. Even if you don’t spot any telltale symptoms of nitrate poisoning, you may find affected fish suddenly die. If you’re not aware of high nitrate levels in your tank and introduce new fish to replace dead ones, these new additions may quickly perish from the shock of being exposed to nitrate-rich conditions.
What Causes High Nitrate Levels?
There are many causes for high nitrate levels in aquariums, but there are four main contributing factors you need to look out for. One of these is overfeeding. If you are providing your fish with more food than they can realistically eat, much of this food will go untouched. These food particles than rot and dissolve within the water, increasing nitrate levels. If your fish are consuming more food than they need, they will also produce a considerable amount of urine and faecal waste. This will also contribute to high nitrate levels. You face similar issues if you have overstocked your tank.
More fish means more waste is being produced and, if you have a tendency to add more food than is required to the water, there will be far more untouched food matter lying around. Many new aquarium owners go overboard when it comes to stocking their tanks. To avoid overstocking issues, start small and only half-populate your tank. If nitrate levels remain in check for a few months, you can then think about introducing new fish to your aquarium.
Another common cause of excess nitrate is a dirty filter. Inexperienced aquarium owners don’t realise that they need to carry out regular cleaning and maintenance of their tank filters to ensure they are working efficiently. The media within a filter only serves to trap waste material. Eventually, the filter media will become saturated. Once the media has become saturated, the filter will not be able to do its job until it has been cleaned or replaced entirely.
If you’re using aquatic plants as a natural aid to water filtration, you need to be careful that they’re not adding to the nitrate problem. Although a healthy aquatic plant will indeed help keep nitrate levels low, poorly maintained plants with dead leaves and appendages will only kick out more decaying matter into your aquarium.
How to Lower Nitrate Levels
Thankfully, there are many solutions for keeping nitrate levels in check. Many aquarium filters are designed to efficiently absorb nitrate from tank water, while biofilters are also effective at denitrifying tank water. However, these will only tackle existing nitrate, rather than remedy the cause. Ultimately, you will need to adhere to a strict water change schedule to keep on top of nitrate levels. However, swapping out a significant amount of existing water for new water is not a great idea. If your fish have become acclimatised to nitrate-rich water, replacing a significant amount of their environment with freshwater can prove harmful. If you’ve tested your tank water and nitrates are high, replace water in small volumes gradually.
Preventative Measures
The best way to combat nitrate is to prevent it becoming a real problem. Regular maintenance is the best way to keep nitrate levels low. You should also look at your feeding routine. Be sparing when adding food to your tank. Once you’ve peppered the aquarium with food, time how long it takes for your fish to consume the food you’ve added. If you’re fish are taking longer than a couple of minutes to consume all the food particles you’ve added to the aquarium, you’re probably using too much food. Instead of adding a large amount of food to your tank once a day, consider two or three smaller feeds daily.
This will allow you to keep an eye on untouched food waste more accurately. A daily inspection of your tank will also help you prevent issues that will lead to nitrate build-up. If you spot any large pieces of uneaten food, remove them from the tank. If aquatic plants have withered and left dead steams or leaves on your substrate layer, get rid of them before they start decaying and releasing nitrate into the water.
If you have a freshwater aquarium, regular water changes are essential at tackling high nitrate levels. A weekly water change should allow you to keep on top of nitrate issues, although more regular changes be required for larger tanks. You should also ensure you have a ready supply of water testing kits at your disposal to keep an eye on chemical levels within your tank water. Regular water changes are not always an option for saltwater and marine aquariums. However, you can overcome nitrate problems by requiring on advanced biofilters and aquatic plants that will help help keep nitrate levels low naturally.
Maintaining healthy water conditions and ensuring nitrate levels remain low can be difficult for new aquarium owners. However, carrying out some basic maintenance and adopting a few best practice techniques will ensure that your fish and aquatic plants thrive in the long term.
