Ammonia/pH Aqua Sensor

Ammonia/pH Aqua Sensor

The Ammonia/pH sensor enables visual monitoring of toxic ammonia (NH3) and pH levels in aquaria water on a continuous basis. Simply attach it in a visible location with both sensor pads completely immersed. With initial use, wait 15 minutes for the NH3 sensor to hydrate and up to 24 hours for the pH sensor to hydrate before making first reading. Thereafter they respond quickly (1-5 minutes) to changes in NH3 and pH.

“This sensor can show the presence of ammonia when other tests can’t.”

Match the sensors to the respective color-gradient indicator charts to readout the ammonia & pH concentration. An included larger color-gradient card enables a color-match with more resolution. The ammonia sensor is accompanied with a pH sensor, which provides further valuable information about water quality – and the risk of NH3 toxicity your aquatic life is exposed to. With pH measurements, the Total Ammonia in the water can be determined, thus supplying additional information about your water quality.

“Ammonia is the number one killer of all aquatic life.”

Key Features
  • Continuous monitoring – 24/7, the ammonia level can be determined with a quick glance.
  • Fresh & Saltwater – compatible in any aquatic environment.
  • Ammonia detection – NH3 is directly measured, which is the toxic concern, rather than the ammonium (NH4+) ions in water commonly detected by other tests as an indirect indicator of the potential risk of NH3 poisoning.
  • Long lasting – up to 1 year for ammonia sensor & 1-3 months for pH sensor.
  • Unaffected by chemicals – Ammonia & pH stabilizers and other chemical agents won’t affect the performance of the sensor.
  • Removable pH sensor – convenient, interchangeable pH sensors (2 included in package).
  • NO chemicals, test kits, sampling of water, or procedures are needed.
  • Highest NH3 sensitivity – capable of detecting extremely low concentrations (0.005 ppm), this sensor offers more protection of aquatic systems. Earlier indications of increasing levels enable better management of water quality, more time for corrective action, and less risk of exposures to injurious NH3 levels.
  • Unobtrusive – won’t disrupt the aesthetic appeal of your aquarium (measures only 1.00″ x 3.75″).
Discussion of NH3 & NH4+

Unlike most ammonia testing systems, the ammonia/pH aqua sensor measures only the toxic form or free-ammonia (NH3) in aquatic environments. Thus, it is the best direct indicator of the toxicity your aquatic life is subjected to. Ammonia (NH3), the toxic form, is normally in far lower concentrations than the much less harmful Ammonium ion (NH4+). The ratio of NH3 to NH4+ changes with temperature and pH; a rise in pH or water temperature causes increasing amounts of toxic NH3 (See Total Ammonia Calculation for further information).

Therefore, in addition to the ammonia, it is valuable to know the pH of the water and its ammonium NH4+ content. It’s important towards fully understanding your aquatic system’s potential risk level. Realize that a sudden rise in pH can cause a significant conversion of NH4+ into NH3 resulting in toxic levels. With an ammonia and pH measurement, one can derive the water’s Ammonium content, as well as Total Ammonia (NH3 plus NH4+).

Note: most other test kits actually measure Total Ammonium, even though they are routinely identified as ammonia tests.


The ammonia sensor is normally yellow when no ammonia is present (the desirable state). Exposure to increasing levels of ammonia change the sensor to shades of green, grey, and then violet. When ammonia decreases, the sensor color accordingly reverts back to yellow; but the change is often slower. Changes away from yellow indicate that potentially hazardous ammonia is present. Little, if any, ammonia is found in a healthy system. Even 0.01 ppm of ammonia can be lethal for some organisms. Take appropriate action to reduce ammonia and alleviate the toxic risk.


The pH (Potential of hydrogen) identifies the alkalinity of your aquaria’s water. The sensor’s range of sensitivity enables use with either freshwater or saltwater aquaria. Color-match the pH sensor with its respective color-gradient much like the NH3 sensor. The pH sensor is normally yellow when alkalinity is low. Consult your local fish expert to determine the proper pH range for your particular aquaria.

Ammonia Sensor Sensitivity

This ammonia sensor is designed to be highly sensitive to ammonia. It can detect ammonia (NH3) at 0.005 ppm. This provides the earliest possible indication of ammonia increasing in your system; thus the highest level of protection, lowest risk of toxic injury, and the greatest margin of safety for taking corrective measures.

Pacific Sentry’s sensor can show the presence of ammonia when other products may not. Do not confuse the sensor’s ammonia indication with other test products that measure Total Ammonia. They will have much higher values in the ppm range.

Usage Information

A goal of ours was to make the ammonia/pH sensor unobtrusive in your tank; the color indicators with the sensors are intentionally small. The separate hand-held color gradient card, with larger color indicators and additional values, permits more accurate sensor readouts. The in-tank indicator chart for the ammonia sensor can also be removed for absolute minimal disruption of aesthetic appeal to your aquarium.

Sensor-color perception and matching is influenced by the nature of the light used for viewing. Lighting for aquaria have different spectral outputs. We recommend viewing under fluorescent lighting.

Sensor Usage Life

The useful lifetime of the sensors can be influenced by a number of factors that vary from system to system. Though unable to predict for your particular conditions, the pH sensor should be useful for 1-3 months before needing replacement and the ammonia sensor can last up to a year. Gradual fading of sensor colors over time is to be expected. Exposure to direct intense lighting can influence this, and is best avoided.

If colors lighten, you may prefer to use the gradient-color charts on the included color card. They show fading color gradations of diminishing intensity to aid in matching the sensors. The pH sensor can be easily replaced with the interchangeable pH sensor strips provided with the sensor. When its color appears too light after extended use, simply remove suction cup, push the old sensor up and out of its holder and then drop in the new pH sensor.

Sensor Care

Avoid damaging the sensor by fingers, fish, or other types of physical contact. Touching with fingers may discolor the sensor and affect performance. Sensors can be taken out of water and even dried without harm. However, they need time to re-hydrate again when returned to use.

Get to know your system

You will quickly become familiar with the sensors’ typical colors for your system’s water quality. With a glance, you should be able to identify its status; whether it is in normal range, or if changes are occurring. Rising NH3 or pH changes indicate your water quality is changing; some environmental aspect is no longer in ideal balance. When setting up new aquaria, or working with large water changes, an increase in NH3 is expected. The system is undergoing conditioning. As the environment develops proper balance, NH3 declines and the pH will return to normal levels.

Disruptive changes in ideal water balance include: increasing the quantity of fish, overfeeding, reduced efficiency of the filter, changes in pH or salt content, water treatments, or anything affecting the balance of important bacteria. When the ammonia/pH detects rising NH3 and/or pH, giving warning of potential toxic risk, consult your local specialist or seek other professional advice for corrective action. Proper Ammonia and pH levels differ depending on your type of aquarium and organisms.

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Ordering Information

Buy your sensors online by clicking the “add to cart” button on the Products page or call (425)-229-9701 and talk directly to a representative to place an order. Custom fabrication requests are also welcomed; call or email for details. We will gladly work with you to design the best solution that meets your needs.

Shipping & Handling
in the United States

Products will be shipped within 2-4 business days. Ground shipping usually takes 3-5 days depending on shipping destination.

International Shipping
(Including Canada)

International shipping and handling depends on the specific country. Please email Customer Service at with your shipping address, product of interest and desired quantity. A shipping estimate will then be provided.

Our Return Policy

If you are not satisfied with our product for any reason, please return it within 14 days of receipt for full refund.

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