Nitrogen cycle: In layman’s terms

What is the nitrogen cycle?

At its most basic level, the nitogen cycle is this: Fish poo and rotting vegetation gives off toxins that are harmful, so you need to convert it to something less harmful, then when you’ve done that you need to convert that to something even less harmful, then you can get rid of it. Your allies in getting rid of ammonia and nitrites are the beneficial bacteria in your filter and the plants in your aquarium.

What causes ammonia in an aquarium?

Ammonia is the main waste product of fish and is excreted by their gills continuously. Waste like rotting vegetation, fish poo, excess food and dead fish also give off ammonia. Basically ammonia (NH3) is bad news for your fishtank. Not only will it make your fish sick, it will also encourage algae growth. Specialists like Swell UK offer a range of ammonia and nitrite test kits and treatments and we are just a call away for advice. In a massive body of water like a lake, the ammonia would dissipate quite quickly, but in your fish tank it needs a helping hand. Especially in a new aquarium that hasn’t had time to mature, your ammonia levels will likely run high. Bacteria called nitrosomonas cause the ammonia to convert to nitrites (NO2) which is better than ammonia but still bad for your fish.

How can I remove ammonia from my aquarium?

In a mature fish tank you will have different levels of filtration – chemical, mechanical and biological. Here is where the biological filter comes into play in the nitrogen cycle. Your filter acts as a breeding ground for beneficial bacteria. The bacteria feeds off the ammonia and nitrites and consumes the oxygen. When the water passes back through the filter into your aquarium, the amount of ammonia and nitrite has been reduced to less harmful nitrates. So begin by testing your water routinely for ammonia levels and nitrite levels with an Ammonia Test Kit and nitrite tester

What are the signs ammonia is high in my fishtank and what can I do about it?

If your fish look distressed, start breathing rapidly, or are gasping for air, it could be that you have excess ammonia levels. A product like API Ammo Lock will help you out by ‘locking down’ the ammonia. The Ammo Lock will detoxify the ammonia by removing the chlorine and chloramine so the biological filter can reduce the ammonia. Seachem AmGuard is also ideal for removimng toxic ammonia along with chlorine and chloramines. In nature nothing that exists can ever be made non-existant, all that can happen is that it changes its state. Just like burning wood reduces it to charcoal or ash, similarly you can’t made ammonia or nitrite disappear, all you can do is make it into something else, and that something is nitrate (NO3) which again, is less harmful that ammonia but still not what you want in your tank.

What should my ammonia levels be?

Your ammonia and nitrite levels should always be kept to zero in a mature tank. Nitrates are still harmful but to a lesser extent, and luckily they can be removed with water changes or Purigen. While running through the nitrification cycle, don’t add more fish, change your filter media or overfeed your fish – you will only make the situation worse.

Can plants help keep nitrates down?

Yes. Plants will see the nitrates as food – nitrates are Baby Bio for aquarium plants. This is where the cycle comes full circle. Plants (rotting vegetation) can be the cause of the ammonia spike, but they can also be the solution. Vegetation causes ammonia and nitrites, this is then converted to nitrates and are absorbed by plants.

Apart from making my fish sick, what other side effects of ammonia and nitrates are there?

Unfortunately the kind of plants you want are not the only thing that feeds off nitrates – algae also thrives in a nitrate rich environment. So an abundance of algae is also a tell-tale sign that your nitrate levels may be too high.

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Georgina is a member of the Swell UK marketing team and has been keeping tropical fish for a number of years now. Her favourite fish being the stunning, male Siamese Fighting Fish. She is also looking to expand her existing collection to include keeping saltwater fish as well. Her other pets include Bengal cat, Walter, and Labrador and Rottweiler cross, Presley.


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