Donít let high nitrates get you down! - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 09-30-2009, 10:19 AM Thread Starter
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Donít let high nitrates get you down!

How do I get my nitrates down? It’sa question asked every day and sadly there is no quick and easy answer. What are nitrates? Nitrates are an end product of the reaction that takes fish waste in the form of highly toxic ammonia breaking it down to produce nitrites which in turn are acted upon by a different species of bacteria to produce nitrates. Each step of this reaction requires oxygen. In marine aquariums we are constantly striving to get lots of filtration and circulation to improve the environment for fish and invertebrates alike. This tends to create an oxygen rich environment which favours the quick and efficient conversion of ammonia to nitrite and nitrite to nitrate. So in short, modern aquariums are almost designed to produce high levels of nitrates.

Until recently water changes were thought to be the best way of getting rid of Nitrates. Are water changes the answer? Water changes are an effective way of diluting pollution in your aquarium but they can be a long joyless method of trying to get rid of those pesky nitrates. Many people have commented on doing large water changes, testing the nitrates afterwards, seeing an improvement only to find the nitrates are back up again a few days later. In many cases nitrates only become a priority when they have been at a persistently high level for a

long time.

Does anything eat Nitrates? This article started off by saying nitrates are an end product. Under normal aquarium conditions nitrates accumulate as they cannot be converted into anything else. However in certain conditions nitrates can be broken down by bacteria to produce nitrogen gas. This is not an easy step, requiring extremely
low oxygen levels, and to survive the bacteria remove the oxygen from nitrates. This is essentially how nitrate filters work, creating an enclosed anaerobic environment were the process takes place. It also occurs at the heart of every piece of live rock. Living rock, we love it! Some of the best aquariums around the world are filtered using live rock, a protein skimmer and little else. This shows the ultimate importance of both of these elements. The purpose of a biological filter media is to provide a large surface area for bacteria to colonize. Each piece of live rock possesses a massive surface area and acts as a perfect home for bacteria. Its external surface promotes aerobic bacteria that process ammonia and nitrites, whilst its interior surface promotes anaerobic bacteria that process nitrates. These two types of bacteria work hand in hand and can break down large quantities of fish waste as long as you take care of your live rock. Live rock is all the biological filtration you will ever need.

Reducing nitrate production: Wash your food When feeding frozen food it’s important to realise the freezing process is destructive. Legs pop off, juices flow out, and there can be a lot of waste built up in the frozen liquid around brine shrimp or mysis. Defrost your food in a cup of aquarium or RO water, give it a stir and then strain of the meaty bits, this way the fish only gets fed what they need..

Feed wisely Watch how much you feed and make sure you feed good quality foods. Frozen foods are good quality but they can input more waste than you bargained for. Alternating frozen foods with a good quality flake food gives you the best of all worlds.

Wash your filters This might get people running and screaming, but you should wash any foams in your filter under tap water (ideally followed by a rinse in RO water) every week. This goes against everything fish keepers are told from the very first time they buy a goldfish. But in this situation we do not want the foams to grow
bacteria, remember the live rock should do all the biological work. The foams should be used as mechanical filters only, that is they catch particles from the water, excess food etc which then get flushed down the sink. No bacteria grow on the surface and therefore no nitrates are produced.

Remove biological media Again this seems like another loony tunes suggestion but most biological filter media is too efficient. The high flow rates in external filters coupled with efficient biological media create effective nitrate producing machines, The bacteria that were growing happily on the live rock are seduced into moving into a new home in your hi tech filter media and lose their link with the anaerobic bacteria in the middle of the live rock. As long as you have a sufficient amount of live rock in your tank the process should be relatively painless You should plan to remove a few bioballs or ceramic rings every week or every other week to keep any disturbances to a minimum. It’s not a bad idea to keep an eye on your water quality whilst doing this.

Protein skimmers rule If you haven’t already got one, get one! Their job is to remove raw sewage like material straight from the aquarium. If you skimmer is stripping out lots of this gunk then the bacteria don’t even get a look in and you have reduced another area of nitrate production. Maintaining your skimmer is key, any sludge that builds up on the neck of the skimmer will dramatically reduce its performance as will any lime scale build up
inside the pump or in the air intake .In a healthy system with a correctly matched skimmer you should be getting between one and two cups of dark brown liquid a week. {mod comment: The amount of waste removed by the skimmer depends on the amount of dissolved organic compounds produced in your specific aquarium. Levels will vary greatly from one tank to another. - Pasfur} Aim to clean the cup and the neck once a week, whether they are full or not and look at cleaning the pump once a month. Also bear in mind water parameters can affect the performance of your skimmer, pH is a good example and maintaining it correctly keeps the skimmer at full throttle. pH and KH can have an effect on the growth rate of bacteria so keep a close eye on both.

{mod comment: Parts of this post have been edited or removed - Pasfur}

Last edited by Pasfur; 10-03-2009 at 06:47 AM.
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post #2 of 3 Old 09-30-2009, 10:54 AM Thread Starter
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Don't let high nitrates get you down! (Part 2)

Better nitrate removal This is often the more difficult side of the
equation to accomplish, so make sure you have all of the methods of reducing nitrate production in place before hand.

Waft you rock
Everything so far should be telling you that live rock is the real champion in all this. It is important to keep this investment working in peak performance. To do so you need to get your hands wet and waft you hands over the rock work, you should see plumes of dust flying off. This is silt that blocks up the “pores” of the live rock and stops it from doing its job properly. Wafting cleans the live rock and transports the silt towards your filter were it can be dealt with.

Clean your bottom Remember that the substrate can be at the
root of many nitrate problems, so ensure that there is no detritus in or on the sand. In severe cases it may be an option to remove the sand all together and replace it once the nitrate levels are under Control.

Full steam ahead Increasing the flow rate in your aquarium can work wonders for reducing levels of organics including nitrates. Ideally you need to turn your tank volume over 20 to 30 times per hour,
add up all the flow rates of the pumpsand power heads in your aquarium and see how close you get. Try to get a random flow dynamic going in the aquarium, use a wave maker or even change the position of your power heads on occasion.By holding a power head and directing it over the rocks you can use it to “blow the cobwebs away” lifting detritus up and letting your filter deal with it. Boosting your flow rate directly improves the health of your fish and corals, it also carries more of the waste that can build up in the aquarium to the filtration system. Less detritus clogging your live rock means it can work more efficiently and chew up nitrates at a faster rate.

It’s often the case where despite your best efforts, the fish are too greedy or you love your fish too much and have squeezed one or two too many into your aquarium. In this case nitrate filters are valuable tools and if set up correctly you can see the nitrates tumbling in a very short
space of time. A nitrate filter may have 100ppm of nitrates going in and zero ppm on the way out, the down side is they can be costly and tricky to set up correctly.

No such thing as good algae?

One of the more natural methods of nitrate removal and one that has been used for Decades is the use of macro algaes such as Caulerpa and Chaetomorpha. These thrive on nitrates as well as phosphates and if managed correctly will provide you with a nutrient poor reef, in other words mimic nature. They do need good flow rates as well as lots of lighting and they can take over if left to grow freely in your display tank which may damage corals. The best way to grow them is in a separate tank or sump were they can be managed to greater effect. Many people employ a reverse photoperiod (switch the
lights on over the algae when the main lights go off) this helps to reduce the daily pH swing you can get in a reef aquarium. The key to any macro algae farming is regular harvesting. The algae sucks up nitrates by growing. If it fills the tank or sump, growth slows down and so does nitrate removal. As a rule of thumb, the algae should grow vigorously enough for you to harvest 50% every two weeks

Chemical filtration Whilst effective in its own way, this last group of nitrate removal methods is often the least economical. Methods of chemical removal act by absorbing nitrates. The down side to this is that once they are exhausted that’s it you have to add more. Many products such as polyfilters and Amquel {mod comment: Amquel does not claim to remove Nitrate. - Pasfur} are fantastic at absorbing or converting organics such as nitrates in emergencies but are a costly way of achieving your long term goal. They all have their uses but if you choose to base your method of nitrate control on the topics discussed so far you are likely to have a more reliable and self sustaining system which ultimately means more time enjoying the marine hobby and less time working on it.

{mod: Portions of this post have been deleted. - Pasfur}

Last edited by Pasfur; 10-03-2009 at 06:52 AM. Reason: advertising
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post #3 of 3 Old 10-03-2009, 06:59 AM
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The above posts provide some very useful information for the beginning marine hobbyist and are a great read for those seeking a beginning level introduction to marine filtration concepts.

I want to add some additional comments about Nitrate removal. The most effective method of nitrate removal includes the use of live rock and a deep sand bed. Aragonite sand at depths between 4'' and 6'' is ideal for the growth of bacteria that convert Nitrate into Nitrogen Gas. Nitrogen Gas leaves the system naturally, and Nitrates are removed directly from the water. In such systems with proper sand depth and water flow, there is very little risk of detritus accumulation.

In systems with lesser depths of sand, it is strongly recommended that the sand bed not exceed 1'' in depth. The reason for this is that depths between 1'' and 4'' tend to accumulate detritus without the proper bacteria in place to process this waste. In these situations, it would be more effective long term to use 1'' or less of sand and increase the amount of live rock in your aquarium. As mentioned in the above article, live rock provided effective denitrification. As such, amble amounts of live rock are very important in systems not utilizing a deep sand bed for denitrification. My 180 FOWLR is a perfect example of this situation. I run a 1'' sand bed, have a heavy fish load, and my nitrates remain under 5ppm.
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