Category: How To Guides

About Ammonia

Ammonia Quick Facts

  • Ideal ammonia level is always 0 ppm — any detectable amount is a concern
  • Higher pH and higher temperature increase ammonia toxicity
  • Ammonia above 6 ppm is a critical emergency — perform a 75% water change immediately

Any time organic matter is introduced to an aquarium — including fish, invertebrates, live plants, or live rock — ammonia will be produced. Ammonia is the primary waste compound in any aquarium and the starting point of the nitrogen cycle, the biological process by which beneficial bacteria convert harmful waste into less harmful compounds. Understanding and managing ammonia is the foundation of a healthy tank.

Ammonia and the nitrogen cycle

When setting up a new tank, it is normal to see ammonia levels rise during the cycling period — the initial weeks when beneficial bacteria are establishing themselves in the filter. Rather than relying on ammonia-removing products, which only address ammonia already present in the water and can’t affect future ammonia that fish continuously produce, adding nitrifying bacteria is a more effective long-term approach. Nitrifying bacteria establish a biological filter that converts ammonia on an ongoing basis. Once that filter is established, it will continuously convert ammonia on its own, keeping levels in check.

Why ammonia is dangerous

Ammonia is acutely toxic to fish and invertebrates, and lethal levels can accumulate rapidly in the absence of healthy, established beneficial bacteria. Making things more complicated, ammonia’s toxicity isn’t fixed — it shifts depending on the pH and temperature of your water.

Ammonia exists in two forms: unionized ammonia (NH₃) and ionized ammonia (NH₄⁺, also called ammonium). NH₃ is the more toxic of the two — it passes through fish tissue more easily and causes damage at lower concentrations. NH₄⁺ is less toxic but still harmful at elevated levels. The balance between the two shifts with pH: as pH rises, more ammonia converts to the toxic NH₃ form. For example, an ammonia reading that is tolerable at a pH of 7.8 could be lethal at a pH of 8.4. Higher water temperatures also push the balance toward the more toxic NH₃ form, compounding the risk.

The practical takeaway: the same ammonia reading can mean very different things depending on your pH and temperature. In saltwater tanks with naturally higher pH, this is especially worth keeping in mind.

When ammonia becomes a problem

Ammonia is expected during a new tank cycle, but it can also spike in established tanks when maintenance lapses. Skipping water changes, a dirty filter, an overcrowded tank, or the use of certain medications that disrupt the biological filter can all cause ammonia to rise. Any fish death or illness should prompt an immediate ammonia test.

Testing and target levels

Ammonia is measured in parts per million (ppm). The target is always 0 ppm — any detectable amount should be taken seriously. Test regularly as part of your monthly routine, and immediately any time fish appear stressed or a death occurs.

Signs of ammonia stress in fish

  • Rapid gill movement
  • Clamped fins
  • Bacterial infections
  • Mortality

Corrective actions

Great, slight modification and this is what I’ll use:

In all cases of elevated ammonia levels, after completing the steps below, add an ammonia remover like Fritz Rescue A.C.C.R. or Fritz Complete to treat ammonia currently present, then add nitrifying bacteria (FritzZyme® 7 for freshwater or FritzZyme® 9 for saltwater) to fortify your biofilter.

  • 0.5–1 ppm — Reduce feeding, clean the filter, and siphon the substrate to remove excess debris
  • 2–3 ppm — Stop feeding temporarily and perform a 25% water change. Clean the filter and siphon the substrate
  • 4–5 ppm — Perform a 50% water change and follow the steps above. Consult your local aquarium dealer to help identify and correct the underlying cause
  • 6–7 ppm — Perform a 75% water change, follow the steps above, and consult your local aquarium dealer right away

Related Articles

The Complete Nitrogen Cycle

Preferences of Nitrifying Bacteria

Aquarium Maintenance Tips

The ABCs of Water Quality

About Salinity

About pH

About Nitrites

About Nitrates

How to Cycle a Freshwater Aquarium with FritzZyme®

Introduction

This is an in-depth guide on how to best use FritzZyme nitrifying bacteria (FritzZyme 7 or FritzZyme TurboStart 700) to establish a healthy, stable biofilter that cycles your new aquarium or help re-establish an existing system’s biofilter that has “crashed” or needs fortification. If you are cycling a saltwater tank, click here.

The ammonia, or nitrogen, “cycle” is the process of ammonia (NH₃) being oxidized by Nitrosomonas sp. bacteria into nitrite (NO₂⁻), followed by the produced nitrite being oxidized by Nitrobacter sp. bacteria into nitrate (NO₃⁻). These processes can happen simultaneously, continuously and are influenced by water parameters.

Making sure your water is ideal for Nitrifying bacteria growth will reduce the amount of time needed to establish a healthy and stable biological filter.

In this article

Ammonia comes from fish waste, uneaten food and other decaying organic matter.

The bio filter (nitrifying bacteria) converts toxic ammonia to less toxic nitrite then to even-less harmful nitrate.

Nitrates are removed by regular water changes or consumed by live plants.

Prepare your water

FritzZyme nitrifying bacteria can be used with tap water but the water must be conditioned first. Fill your aquarium with water and add a water conditioner like FritzGuard, Fritz Complete or Fritz Rescue A.C.C.R.) to remove chlorine and chloramines. These two chemicals are toxic to bacteria so they must be neutralized before adding FritzZyme bacteria. FritzZyme is a biological product and does not dechlorinate water.



If using RO/DI water, it’s to add a product like Fritz R/O Recharge to replenish minerals, electrolytes and buffering capacity.

Measure and adjust water parameters

Your water parameters are very important to maintaining a healthy population of nitrifying bacteria. Just like fish and other aquatic life, FritzZyme bacteria will grow and thrive in the right environment. Most issues with nitrifying bacteria performance are due to one of the parameters below being out of range.



The ideal parameters table on this page are where the Nitrifying Bacteria in FritzZyme 7 (Freshwater) will perform the best. The preferences for most freshwater aquatic species will fall within these parameters or very close. Nitrification will still occur outside of the ideal range, but may be slowed. Far outside the range, where noted, nitrification will stop completely.

Ideal parameters for FritzZyme® 7 nitrifying bacteria

Parameter
Range
Notes
Temperature
77-86° F (25-30° C)
pH
7.3 – 8.0
Nitrification is inhibited below 6.0
Salinity
0 — 6 ppt (1.000 to 1.0045 sg)
Active up to 15 ppt (1.011 sg)
Alkalinity (KH)
minimum 4.5 dKH or 80 ppm KH
Phosphate
above 0 ppm
If phosphate is not present in any amount, nitrite conversion will stop

Water parameter details

Temperature

The bacteria grow the fastest and perform the best in temperatures from 77-86° F (25-30° C). Below this range, you can expect the bacteria to continue to work, but the nitrification process will become slower as the environment gets colder.

PH

The average pH range for optimal nitrification is 7.3-8.0. Above or below this range, you can expect the bacteria to continue to work, but become slower. Nitrification is completely inhibited below pH 6.0.


Need to raise pH? Try Fritz pH Higher

Note: All ammonia in a system that is below pH 6.0 is ionized into its non-toxic form of ammonium (NH4+). Ammonium is itself is generally safe for livestock, however as pH increases above 6.0, the ammonium present will converted to toxic ammonia and can quickly kill any livestock if not addressed with added nitrifying bacteria, a water change, or an ammonia-binding product like Fritz A.C.C.R. or Fritz Complete.

Alkalinity (KH)

Alkalinity is crucial for the conversion of ammonia to nitrite. A small amount of KH is consumed during nitrificaiton, and can quickly become a limiting factor if not maintained above a minimum level of 4.5 dKH or 80 ppm KH.

Over time, alkalinity will naturally decrease and must be added with a product that raises KH, or a water change using source water with a sufficient KH level. A low KH level can also lead to instability of pH. A large swing in pH in a short period of time will negatively affect your livestock, as well as your biological filter. 


Need to raise KH? Try Fritz RO Recharge, or Fritz Rift Lake Cichlid Buffer.

Phosphate

The phosphate level should always be maintained above 0 ppm. Phosphate is necessary for Nitrobacter sp. bacteria to convert nitrite to nitrate and is consumed in the metabolic process. If it is depleted, nitrite conversion will stop. This is referred to as “Phosphate Block.”

Need to increase Phosphate? Use a phosphate-based buffer like Fritz pH Neutralizer, or a water change with dehclorinated tap water which typically contains phosphate.

Salinity

Freshwater systems should use FritzZyme 7 or FritzZyme Turbo Start 700. Saltwater and reef systems should use FritzZyme 9 or FritzZyme TurboStart 900. The bacteria strains in each formula are optimized for their specific freshwater or saltwater environment and are not interchangeable.

Brackish Systems

Most brackish systems should use the freshwater formulas of bacteria, FritzZyme 7 or Turbo Start 700. These freshwater strains of bacteria are fully functional in systems from 0 – 6 ppt (1.000 to 1.0045 sg). Above this range, you can expect the bacteria to continue to work, but the nitrification process will become slower with higher salinity up to 15 ppt (1.011 sg). If your system is above 15 ppt, we recommend to switch to the saltwater formulas, FritzZyme 9 or Turbo Start 900.

Add nitrifying bacteria

If you’ve prepared your water and have checked the parameters, it’s now time to add FritzZyme Nitrifying Bacteria.

Follow the dose and instructions on the label, or the directions and dose calculator on the FritzZyme 7 or FritzZyme TurboStart 700 product page.

Add an ammonia source

If you’ve prepared your water and have checked the parameters, it’s now time to add FritzZyme Nitrifying Bacteria.

Follow the dose and instructions on the label, or the directions and dose calculator on the FritzZyme 9 or FritzZyme TurboStart 900 product page.

Adding fish/livestock

Adding fish and beginning to feed them normally will start the production of ammonia, and subsequently nitrite, through normal respiration. This is the most simple way to establish your bacterial population to the proper size, and support it passively, since the nitrifying bacteria population will grow to the level of ammonia your livestock is producing.

Adding chemical ammonia for a “fishless cycle”

Adding a dry or liquid ammonium chloride, such as Fritz Fishless Fuel, is an alternative way to add an ammonia source to the system prior to adding fish. Some hobbyists prefer this method if they want to set up and cycle a system in advance of introducing more sensitive species or livestock that may be stressed due to transport. Others prefer to “overbuild” their biofilter if expecting to introduce a heavy bioload.

Note: You should never add an ammonia product to a system while fish are present.

Adding organic matter

Also known as “ghost feeding,” this method involves adding organic material such as flake or pellet fish food which then decays and releases ammonia. While this method can work, Fritz Aquatics generally does not recommend it because it is unpredictable. Different foods break down at different rates, and the amount of ammonia released is inconsistent. Excess decomposing food can also fuel unwanted bacteria, cloudy water, and nuisance algae.

Note: The ammonia concentration needed for the cycling process is very minimal. Any detectable level below 4 ppm is sufficient.

Monitor the cycle progress

Every system will proceed through the ammonia cycle at its own pace. The only way to know what stage the cycle is in is through regular testing of the water parameters.

Testing Ammonia

The ammonia concentration during the cycling process does not need to reach or remain at a specific level. Any detectable level below 4 ppm is sufficient to start the cycling process. Try the Fritz Ammonia Test Kit.

Testing Nitrite

Nitrite is produced from ammonia being oxidized by nitrifying bacteria. The level of nitrite during the cycling process will vary, as it can increase from bacteria processing ammonia, but simultaneously decrease from bacteria processing the nitrite into nitrate. Try the Fritz Nitrite Test Kit.

Testing Nitrate

The nitrate concentration will indicate if the cycle is progressing as expected. The presence of nitrate indicates that the bacteria are performing properly and the tank is cycling. The amount of nitrate at the end of the cycle does not need to reach any specific level, any detectable amount is an indication that the cycle has matured and the biofilter is stable.



Nitrate is the end product of the cycle and is not harmful to livestock in low concentrations. You will see the concentration build up slowly over time. Regular partial water changes will reduce the Nitrate concentration and keep it in check. It’s recommended to keep a Nitrate level below 20 ppm. If your nitrate level is consistently high, consider increasing your water change frequency or reduce feeding. Live aquatic plants can also consume excess nitrate.

Try the Fritz Nitrate Test Kit!

How long will it take?

Once your system is managing the ammonia and nitrite and keeping them at undetectable levels, the tank is considered “cycled.” For most new systems, FritzZyme 7 will become established and complete the cycle in 7-14 days. FritzZyme Turbo Start 700 can become fully established in as little as 3-4 days.

Stocking your system

Both FritzZyme 7 and TurboStart 700 allow safe, immediate introduction of fish to a new aquarium. With a reasonable number of fish and ideal parameters, ammonia and nitrite levels should remain well below the level that is toxic to fish.

Do not overstock or overfeed, monitor water parameters and allow the system to complete the nitrogen cycle and stabilize before adding additional livestock. This approach supports long-term tank stability and healthier fish.