High Ammonia, Nitrite and Nitrate in my new pond – Help!

Andrew HodgesWater QualityLeave a Comment


High Ammonia, Nitrite and Nitrate in my new pond

If you have recently built a new pond, filled it with filtered or treated, clean, fresh water and added a selection of beautiful koi carp or other fish, you may be struggling to work out why its all gone wrong!

You have probably spent a fortune on a state of the art pond filter and all the bells and whistles, but the fish are not happy, worse still some may have very sadly died.

When you test the water ammonia, nitrite or nitrate levels are in the danger zones. I will try to help get you through this phase and explain what often happens with new ponds.

If you are in dire need of help now and have not got time to read the full article, click below to jump straight to the actionable advice. It would probably be wise to come back and read the full article in detail later.

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to Practical Advice

How did your koi carp pond go so wrong?

You may be asking yourself “what did I do wrong?” Or wonder whether you bought the fish from a dodgy pet shop. You may even be thinking that the fish were already sick and unhealthy and that they have polluted your pond.

Those thoughts are perfectly natural, after all, you spent ages researching and designing your pond, it should be perfect. But for some reason, it’s all gone wrong.

The fish, in all honesty, were probably in perfect condition when they left the shop, there are not many serious koi dealers who would risk their reputation by selling sick fish.

Here I will explain the most common yet misunderstood problem facing new koi carp hobbies –

New Pond Syndrome.

The fact is that you most probably have done nothing wrong in the design and construction of the pond. Your pond has just not had a chance to mature – or cycle.

Cycling is the time it takes for your pond, water and filter to transform from brand new separate shiny materials to biologically active water filtration and cleaning plant.

As well as this, the new pond with all of its new materials, the new pumps, filters and liners need to bed in. As they bed in, they all release tiny traces of chemicals into the water, which can add to the stress of the fish.

So what is the cause of the unhealthy pond water?

Being completely honest and unbiased, I would have to say that the biggest cause of new pond syndrome is impatience.

If you are struggling with your pond water parameters as you read, you probably don’t care for my opinions. But did you follow the advice on seeding your filtration system to the letter, or did you, like me with my first pond, buy lots of new fish in week one?

The advice in every koi book or magazine on new ponds always says “give the pond time to mature and allow the filter to cycle fully before adding expensive fish”. But in our keenness to start enjoying our new hobby we rush out and buy fish as soon as the water has filled the pond, it looks so inviting, the fish will be so comfortable!

So what we should have done is add a few small fish, some filter start bacteria if you feel the need and wait. Test the water and add more fish when the water test demonstrate that the biological filtration is starting to mature.

Understand the koi carp pond Nitrogen cycle

Being a practical person, just wanting to crack on and build my pond, I assumed that the pond filter with its brushes and sponges (this was way before drum filters or The Nexus) simply cleaned the water mechanically. I had no idea about the biological processes necessary to maintain healthy water.

I tended, to skip the articles on biological filtration. After all, how could they help me install the bottom drain and get that liner in? I’d read up on that stuff later when I had more time, or so I thought.

One piece of advice that I would give you right now is to read on and learn the Nitrogen cycle; it’s not rocket science. In fact, in essence, it is very simple. It will serve you well in the future.

Stage one – feeding the fish koi food

The first part of the cycle in our ponds, is us putting food into the water. People assume it is the fish which pollute the water, but in fact, they are working to break down the food which we pollute the water with. I’ll explain.

When we place food into the pond it will have a detrimental effect on the water. Uneaten food is the biggest issue in terms of pollution. It has been said that up to 20 per cent of the koi carp food put into ponds goes uneaten!

This food waste is, in fact, a bigger problem than fish poop. Your fish partially break down or use up the food they eat. The fish work as little factories, they break down the proteins in the food to make amino acids required to repair, produce heat and grow.

If you have nothing but fish and water in a container and add food, the fish will convert the food into ammonia, which if not removed and allowed to build up will eventually kill them.

Stage two  – Converting Ammonia to Nitrite

So it is imperative that we eradicate Ammonia. Fortunately we do not have to do a lot, so long as we have an established colony of beneficial bugs in our filter. These beneficial bugs, Nitrosomonas, convert the Ammonia into the relatively less toxic Nitrite.

Nitrosomonas will be present in the pond water as they are abundant in nature. They will, however, take time to multiply and be present in sufficient numbers to deal with the quantities of Ammonia produced by large numbers of koi carp. Hence the build up of dangerous levels of Ammonia in a new pond which as lacks an established biological filter stage.

To assist in the colonisation of bugs in your pond you can add a proprietary filter start product. There are many proprietary brands of filter start available, for new ponds we would recommend Evolution Aqua Pure+ Filter Start Gel.

Nitrosomas multiply relatively quickly converting Ammonia into Nitrite, which although less toxic to fish must also be eradicated from the pond system.

Thankfully there are more helpful bugs on hand, Nitrospira and Nitrobacter, which help us further.

Stage three – Converting Nitrite to Nitrate

High nitrite levels can cause irreversible damage to your fish’s liver, spleen, nervous system and cause kidney damage. You may notice fish gasping at the pond surface or hanging near air stones.

Brown blood disease

High nitrite levels can result in a condition known as brown blood disease.
Nitrite enters the fish’s bloodstream through the gills and prevents the red blood cells from absorbing and transporting oxygen. It turns the fish’s blood a chocolate-brown colour.

Haemoglobin, which transports oxygen in the blood, combines with nitrite to form methemoglobin, which is incapable of oxygen transport. Affected fish can suffocate regardless of the oxygen concentration in the pond water.

Since this is a nitrogen related problem, the most obvious solution would be to reduce the amount of nitrogen put into the system by reducing feeding rates.

The effects of high nitrite can be minimised using sodium chloride NaCl (common salt). Calcium chloride CaCl2 can also be used but is more expensive.

The chloride competes with nitrite for absorption through the gills, maintaining at least a 10 to 1 ratio of chloride to nitrite in a pond effectively prevents nitrite from entering the fish.

Where fish have bacterial or parasite diseases, their sensitivity to nitrite may be greater, and a higher chloride-to-nitrite ratio may be needed to afford added protection from nitrite invasion into the bloodstream.

Many of you will probably be finding this article because you are in despair at the high Nitrite readings in your pond water. The reason is most probably because your pond is still evolving and has become efficient at dealing with Ammonia, but the bugs required for the next stage have not yet established.

Nitrospira and Nitrobacter are exceedingly efficient

Nitrospira and Nitrobacter are many many times more efficient at dealing with Nitrite than Nitrosomonas are at dealing with Ammonia. So why then do we always see such high Nitrite spikes in new koi pond systems.

The main reason for this is that these bugs are much slower to establish within the ponds ecosystem than Nitrosomonas. Even with the addition of filter starting products they seem reluctant to multiply.

Unfortunately, the way to ensure you do not get Nitrite spikes is to establish the filter long before adding any significant fish load. This is accomplished with fishes cycling, which I will explain later. But if you are here because you already have this issue, how can you sort it out right now?

Well, you could try water changes to reduce the stress on the fish, but this will only be a temporary fix and may extend the period required to cycle the filter. As the bugs will only multiply to meet the demand for them to deal with Nitrite.

Some say that the length of time required for Nitrite to harm fish is quite long and sufficient for a filter to cycle, I am not so sure as this will be dependent on many varying factors such as water volume, number and size of fish, type of filtration system and media, etc.

Practical steps to solve high nitrite levels follow, but for now let’s continue with the cycle.

Stage four – dealing with high Nitrate levels in our pond water

In a pond without plants, Nitrate levels will build up over time. In essence, this is a good sign as it shows that the filter system has cycled, meaning that all of the helpful bugs, Nitrosomonas, Nitrospira and Nitrobacter have established in sufficient quantities to deal with the fish load.

Nitrate is relatively harmless to your fish, but it would be preferable to have a zero Nitrate level in your pond water. Water changes can be used to reduce the level of Nitrate.

If you were to add some plants to your pond or add a refugium or separately connected pond containing plants it would help control the Nitrate levels.
In nature a deal of fish waste is dealt with is by plants.

Interestingly plants prefer to use Ammonia than Nitrate, so in a planted pond much of the Ammonia is dealt with at source. Meaning that only limited Nitrite and Nitrates are cycled by our friendly bugs.

In ponds with plants and filter systems, the cycling can happen more naturally as plants and filter work together to establish a biosphere for your fish.


Emergency steps to improve pond water quality

So you have high levels of Ammonia, Nitrite or both in your pond. Your fish look sick and you do not know what to do next.

I am sure you don’t want to hear this, but time is required to build up the bio-film within the pond.

You are caught in a catch 22, if you change the water your filter will not cycle, see above, and if you don’t change the water your fish may die.

As mentioned plants will deal directly with ammonia, so if you are able to add some active growing plants you could buy some time. Water changes will reduce the nitrite and plants could prevent further Nitrite being produced.

  • Add a filter start product

    Purchase a proprietary filter culture and add to you ponds biological filter system.

  • Add some plants

    If possible place some pond plants, perhaps in floating baskets, to your pond.

  • Consider Anoxic Filtration

    Build and add some biocenosis baskets to your pond system.

  • Make water changes

    Make some water changes to reduce the stress on the fish

Anoxic filtration

There is a little known filtration system which was developed by Dr Kevin Novak, which deals efficiently with pond filtration. It is a remarkable and yet very simple system. You can find great detail here.

I have conducted my own tests on this system and will go into full details in the future, lets just say that I was amazed by the results obtained.

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