02/20/2023 | Aquaculture | 9 MINUTE READ

Aquarium Water pH Maintenance

aquarium water

Water quality is often measured with the pH term, which means “power of hydrogen”. The water’s pH refers to the acid-base balance that the solution has. When you measure the pH of a water sample, you’ll receive readings that range from 1-14. Water consists of oxygen and hydrogen atoms. If the water is neutral, it will have the same amount of hydroxide ions and hydrogen ions for a pH of 7.0.

When there are dissolved minerals and chemicals in the water, the balance of ions can change from neutral to acidic, which occurs when there’s a higher concentration of hydrogen ions than hydroxide ions. An acidic solution will have a pH value that’s lower than 7.0. Alkaline solutions occur when the pH levels are higher than 7.0.

If you’re attempting to raise fish in an aquarium, different species have different pH requirements. However, the ideal pH range for fish is anywhere from 6.5-8.0 pH. When pH levels move outside of the optimal range in either direction, the health of the fish can deteriorate quickly. The following offers an extensive look at how to maintain pH levels in aquarium water.

What Is Normal pH in Public Aquariums?

There isn’t a single “normal” pH reading where all fish would be healthy. The many different species of fish originate in oceans, lakes, ponds, rivers, and streams. Each body of water has a different pH range, which means that the fish that grow in these waters become accustomed to the pH levels of a specific body of water.

When it comes to saltwater fish, the ideal pH level is around 8.0. African cichlids are present in lakes with pH values that are higher than 8.0. In comparison, tropical fish from Brazil can tolerate more acidic water that reaches a pH level of 5.5 or lower. Before you raise fish in aquarium waters, you should know the pH readings your fish would be able to tolerate.

Remember that pH isn’t a static measurement. If anything is added to the water, it’s likely that the pH readings would change. In nature, the photosynthesis and plant respiration processes usually cause pH levels to dip at night before increasing during the day. The pH levels could also change if fish are added or removed from the water. The same is true if new water is added or if different biological processes change with the aquarium.

Preferred pH of Common Freshwater Fish

As mentioned before, every type of fish has a preferred pH range that it thrives in. The preferred pH levels for common freshwater fish are:

  • Angelfish: Around 6.5-7.0 pH
  • Clown loach: Around 6.0-6.5 pH
  • Goldfish: Around 7.0-7.5 pH
  • Harlequin Rasbora: Around 6.0-6.5 pH
  • Hachetfish: Around 6.0-7.0 pH
  • Neon Tetra: Around 5.8-6.2 pH
  • Plecostomus: Around 5.0-7.0 pH
  • Silver Dollar: Around 6.0-7.0 pH
  • Tiger Barb: Around 6.0-6.5 pH
  • Zebra Danio: Around 6.5-7.0 pH

How Important Is pH in Public Aquariums?

Substantial pH alterations are challenging for fish that are young or sick. For many species, breeding will only take place in a certain pH range. When creating an aquarium, it’s important to know what the water’s pH levels are, which makes it easier to determine which species of fish the water will accommodate.

While some fish can be healthy in a wide pH range, other species require narrow pH ranges. If you’re moving fish to a new aquarium, it should match the pH levels of the old aquarium. Any sudden changes to the pH level could result in the fish becoming sick or dying off.

How Often Should pH in Public Aquariums be Checked?

When considering public aquariums, pH levels should be properly tested at least one or two times each week, which will allow you to identify if slight changes in pH readings are part of a trend. You should also maintain test results by storing them in a logbook that can be referenced later on.

Since pH levels can differ depending on the time of day, you might obtain different results at different periods of the day even though nothing has actually changed. To mitigate this issue, you should perform tests at the same time each day.

Whenever a fish becomes ill or dies, the water’s pH should be tested. In the event that you treat the tank with medication, make sure to check pH levels at the start of treatment, on the last day of treatment, and one week after treatment ends. If the pH readings are outside the optimal range for fish, take action to change the pH. You should also test aquarium water before buying new fish.

Aquarium Water Quality: Sources of Water

There are four separate types of water, which include municipal water, well water, reverse osmosis water, and softened water.

Municipal/Tap Water

Municipal water is a decent option when you’re creating a freshwater aquarium. However, certain precautions must be taken beforehand. The majority of municipalities use chloramine or chlorine to treat and disinfect drinking water. Chlorine is highly toxic to all species of fish and should be removed from the water before fish are placed in the aquarium.

Chloramine is chlorine that has bonded to ammonia. Both of these substances are hazardous to fish. The process for removing chlorine from water involves aeration, which is a basic water treatment technique. However, chloramine is considered to be more stable, which is why it’s also more challenging to remove from the water. Chlorine is able to be removed by placing a commercial dechlorinator in the water. Make sure that the dechlorinator is able to remove chlorine and chloramine before using it.

Municipal water plant

Well Water

Well water differs considerably from location to location. Even though well water doesn’t have much oxygen, it does consist of high levels of dissolved nitrogen and carbon dioxide. Before you place fish in well water, the water should be aerated within 24 hours before you set up the aquarium.

Keep in mind that certain wells can consist of high amounts of iron or hydrogen sulfide, both of which have proven to be hazardous to fish. Aeration can convert dissolved iron into heavier rust and remove hydrogen sulfide from the water. Once the dissolved iron turns into rust, it’s easy to remove it from the water.

Even if your well water is considered to be safe to drink, it might not be healthy for fish, which is why extra water quality testing should occur to identify nitrite, pH, ammonia, hardness, and alkalinity. You might also discover that the water contains high levels of pesticides or heavy metals.

Different contaminants can require different treatments if you want to get rid of them before placing the water in your aquarium. Even though well water is more affordable than other sources of water, it doesn’t undergo the same amount of testing.

Reverse Osmosis (RO) Water

Reverse osmosis is a technique that pushes water through a semi-permeable membrane in order to get rid of most impurities, which include minerals, nitrates, phosphates, heavy metals, and other types of dissolved solids. While this type of water is great when used in numerous applications, it’s not as effective when placed in a freshwater aquarium.

When used by itself, this type of water lacks some of the ions that fish need to live. Reverse osmosis filters are available for residential homes or industrial facilities. Smaller units that can filter around 50 gallons of water per day can be placed under a sink.

reverse osmosis water system

Softened Water

Softened water is any water where the hardness has been replaced by sodium ions. The primary minerals that cause hardness in water include magnesium and calcium. Some fish and plants are present in water that doesn’t contain much hardness. These conditions are common in the Amazon rainforest. However, it’s not often necessary to reduce the hardness of water in an aquarium.

If, on the other hand, you would like to soften the water, one method that’s commonly used involves an ion exchange resin. When using this technique, water will pass through the resin to get rid of the hardness minerals and release sodium.

After a certain amount of time, the resin will be bathed in a salt solution to wash away the hardness ions and pick the sodium ions back up. The contaminated water will then be discharged, after which the filter can once again soften the water. The salt solution that’s used during this process is sodium chloride.

Should Public Aquarium pH Be Altered?

While there are times when you should alter the pH in your public aquarium, you shouldn’t immediately make changes if the optimal pH for your species of fish is 6.5 but the water has a reading of 7.0. If pH levels haven’t changed much and the fish within the aquarium aren’t showing signs of distress, you should maintain the current pH levels. As touched upon previously, the majority of freshwater fish are safe in a pH range of 6.5-8.0.

If your fish aren’t thriving or pH levels are steadily dropping with each passing day, take steps to resolve the problem. Most pet stores sell products that allow you to lower or increase the water’s pH. If you want to maintain current pH levels, the most important steps you can take include vacuuming the gravel and partially changing the water on a frequent basis.

Over an extended period of time, biological filter bacteria in the aquarium will cause the pH to slowly decrease. This issue can be prevented by replacing the lower pH water with fresh water that doesn’t contain chlorine and has a more stable pH.

If you want to house fish in an aquarium, there are numerous factors that you’ll need to consider to ensure the fish remain healthy at all times. Among the most important considerations is what the pH levels are in the aquarium water. If you properly monitor pH levels and put in fresh water consistently, your fish should thrive.

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Posted by Dominic O'Donnell on February 20, 2023

Sensorex is a global leader in the design and manufacture of quality sensors for water quality and process applications. The company offers more than 2000 sensor packages for pH, ORP, conductivity, dissolved oxygen, free chlorine, chlorine dioxide, UV transmittance and other specialty measurements, as well as a full line of sensor accessories and transmitters. Its expert technical support engineers solve analytical sensor challenges with custom designs and off the shelf products.

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