Ammonia spikes in marine aquaria

by Owen James

Mature marine aquariums should never see ammonia levels rise above 0.1 parts per million (ppm), while a better goal is for it to be undetectable with standard test kits.

If your tank is well-stocked and you feed your fish heavily then you may sometimes see ammonia spike up to 0.2 ppm temporarily, before rapidly subsiding.

Levels of ammonia up to 0.4 ppm or so can be tolerated by most marine fish for 2-3 days. Higher levels will kill some or all of them.

Consistent levels ammonia above 0.1ppm are a concern, and you should investigate and remedy such a situation without delay.

Causes of high ammonia readings

Ammonium is the first product of the nitrogen cycle, which means many problems in your tank are likely to manifest themselves first in an elevated ammonia reading.

Here are some of theĀ  most common causes of a sudden spike:

1. The tank or filter is immature

Fish-only tanks filtered by trickle filters, undergravel filters or external power filters take months to mature. Even if you’ve chosen the right filter for your aquarium, it takes time for the bacterial population to expand and stabilise, not to mention all the other populations living on tank furniture, sand, and so on.

Equally, living rock will die back in a new reef aquarium before it begins to process waste efficiently.

If you introduce fish or other animals before the tank has cycled, you’ll see the ammonia level rise, threatening their lives.

This is why old-time marine fishkeepers used to start their tanks with tough specimens like damsels. Today chemical maturing products can play the same role.

After a few days the ammonia level will fall as the bacteria convert its into nitrite, and in turn into nitrate. If you’ve started with hardly fish or inverts, you may be lucky, but there’s not really a shortcut to speeding up the cycling process.

The same thing will also happen if you add too many new creatures to even a cycled and mature aquarium. Build up your collection slowly.

2. You’ve overfed your aquarium

Adding too much food to the aquarium at once will result in some lying around uneaten, which will swiftly start to break down into ammonia. This is even more pronounced in tanks without heavy protein skimming.

Stop feeding until the ammonia subsides (and the follow-up nitrite). Then feed more carefully in future.

3. Something big has died

In larger, mature aquariums it’s easy to lose a fish without noticing for a day or two, and often the tank can cope without an ammonia spike. But in smaller or newer aquariums, the death of almost any significant lifeform will quickly overwhelm the natural filtration capacity of your tank and cause a spike in ammonia.

Many tank crashes happen like this, particularly when an owner is on holiday. One fish dies and starts to decay, and the resulting ammonia and nitrite kills other fish, making the situation worse.

Be vigilant about checking your fish population every day.

4. The biological filter has been poisoned

Fish-only aquariums where medications are used directly can have their filtration systems compromised by accident.

Copper, which is used to treat whitespot and velvet in marine fishes, can easily damage a bacterial filter bed. Copper-resistant bacteria will in time evolve as treatment continues and the ammonia level will subside, but in the meantime your fish face sub-optimal water conditions as well as whatever disease ails them.

Reduce feeding and consider a big water change. If ammonia levels rise above 0.3 ppm, you’ll have to discontinue treatment.

Aquariums of all kinds can also be poisoned by external chemicals, such as carpet-cleaning fluids or paint fumes. Be extra careful if you’re using a protein skimmer, a trickle filter or if your tank is uncovered.

Some such poisons are biodegradable, others aren’t. Try using a Polyfilter or other resin to remove the poison, and monitor the ammonia level and your animals closely.

5. There’s been a power cut

In a power cut, pumps will fail, water circulation will cease, and animals will become stressed and potentially die, while filter bacteria will be killed off by a lack of oxygenated water.

Animal waste will no longer be broken down properly, while in submerged filters the nitrogen cycle can go into reverse, as anaerobic bacteria convert nitrate back into ammonia.

If you can, draw water through your filter every 30 minutes to keep it alive (by syphoning or similar). Also be glad you bought a battery airpump beforehand to keep water moving in your main tank.

With power cuts that last for over 12 hours, you may need to consider discarding external filters and replacing all the filter media in them.

This will obviously have devastating consequences for your aquarium inhabitants, particularly in tanks without living rock or sand beds, as waste will no longer be properly broken down. You will have to distribute fish to friends and local shops – assuming they didn’t also suffer in the power cut!

Large water changes, preferably from a reservoir of pre-made water, can reduce the ammonia level in proportion to the amount you replace but truly high levels of ammonia require you to remove the fish to another tank until it (and whatever caused it) is brought back under control. Otherwise, some or all your animals will die.

Further reading: Ammonia and the Reef Aquarium by Randy Holmes-Farley

Read the Ultimate Secrets To Saltwater Fish And Invertebrates.

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{ 1 comment… read it below or add one }

Jon Martin 11.23.10 at 3:06 pm

Last friday I took a water sample to local fish store and all tested good. On monday I lost a Flame angel, took another sample and it tested high in ammonia and nitrites. Lost another angel and a tang.
Still have two clownfish and yellow tang left. Did a twenty gallon water change (47 gallon tank) and added Prime as directed. Store could not give any explanation as to the spike, also had a white slime on two of the fish that died. Two of the fish had been in the tank about ten days the third about 21 days. Would appreciate any feedback or help you could give me.
Thank you


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