What Is The Best pH Level For Angelfish? (With Practical Tips)

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Angelfish aren’t particularly messy creatures. They typically consume food in moderate amounts and don’t excrete as much waste as some other fish species.

However, that doesn’t mean you can overlook the water’s quality, especially the pH levels.

What is the optimal pH range for Angelfish? How should you react if the pH is outside this range? How can the pH be adjusted?

Are Angelfish adaptable to varying pH conditions, or are they particularly sensitive to such changes?

In this article, I’ll dive deep into these questions, ensuring you walk away with all the information you need. Let’s get started.

The Best pH For Angelfish

The optimal pH for angelfish is between 6.8 and 7.8. Ensuring this pH range promotes their health and vibrant display.

  • Natural Habitat Reference: Angelfish originate from the Amazon River Basin, where the water pH naturally remains between 6.5 and 7.5.
  • Health Implications: Stability within this pH range helps prevent common diseases such as ich and fin rot, ensuring longer, healthier lives.
  • Breeding Considerations: Breeders consistently observe better spawns and healthier fry when maintaining this recommended pH level.
  • Practical Steps: Regularly use pH testers and adjust as needed with natural solutions like peat moss or driftwood to achieve desired levels.

Also Read: Angelfish Water Parameters

How To Properly Measure the pH Level In Your Aquarium?

To properly measure the pH level in your aquarium, you’ll need a reliable pH test kit or digital pH meter.

Regular testing ensures the well-being of your aquatic pets and the overall health of the aquarium environment. 

  • Test Kit Types: There are liquid test kits and test strips; the former often offers more accurate readings, using color charts to interpret results. I personally use this API Freshwater Master Test Kit (link to Amazon).
  • Digital pH Meters: These devices give instant readings; however, they require regular calibration with reference solutions to stay accurate.
  • Sampling Properly: Take water samples from mid-tank depth, avoiding surface water, to ensure a representative pH reading.
  • Frequency Matters: For stability, test weekly, but during issues or after water changes, test daily until stable.

Why Might the pH Level Drop?

If the pH in your Angelfish tank is too low, it likely results from one of the following causes:

1. Natural Biological Activities

Every aquarium is a living ecosystem, where fish, bacteria, and plants engage in natural processes. These processes can produce waste products that may influence the water’s pH.

  • Respiration Effect: Both fish and bacteria respire, releasing CO2 into the water, which then forms carbonic acid, decreasing pH.
  • Waste Breakdown: As fish waste and uneaten food break down, they release ammonia, which in its conversion to nitrite and nitrate, can acidify the water.
  • Plant Processes: While plants consume CO2 during the day, they release it at night, potentially causing daily pH fluctuations.

2. Type of Aquarium Substrate

The substrate, or bottom layer of the tank, plays a role in pH levels. Some materials release substances that can make water more acidic.

  • Softening Substrates: Peat or certain plant-based substrates can release substances that naturally lower pH over time.
  • Reactive Substrates: Some substrates, like certain soils, interact with water, producing organic acids that push pH down.
  • Lack of Buffering: Inert substrates, like plain gravel, lack buffering capacity, making it easier for other factors to drop pH.

3. Presence of Tannins

Tannins, naturally-occurring compounds found in certain woods and leaves, can influence pH when introduced to the aquarium.

  • Driftwood Effects: Driftwood releases tannins that not only tint the water a tea color but also lower its pH.
  • Leaf Litter: Adding leaves, like Indian almond leaves, introduces tannins which naturally reduce pH, mimicking certain natural environments.
  • Natural Softening: Tannins bind with minerals, reducing water hardness and, in turn, creating a more acidic environment.

4. Using Low-pH Tap Water

Tap water isn’t consistent everywhere; its pH can vary based on regional treatment processes and sources.

Using tap water with a naturally low pH can significantly influence the aquarium’s pH.

  • Regional Differences: In some areas, tap water comes from sources like rainwater or peat-rich grounds, leading to a naturally lower pH.
  • Treatment Effects: Water treatment plants sometimes add substances, like phosphates, which can reduce the pH of the tap water.
  • Regular Additions: Each water change using acidic tap water can gradually lower or maintain a low aquarium pH, impacting the tank’s stability.

5. Buildup of Carbon Dioxide (CO2)

CO2 levels in the aquarium can greatly affect pH. An excessive accumulation of this gas can lead to a drop in pH.

  • Limited Gas Exchange: A lack of adequate surface agitation or a tight-fitting lid can restrict CO2 escape, allowing it to build up and acidify water.
  • CO2 Systems: For planted tanks, hobbyists often add CO2 to promote plant growth, but if not monitored, it can cause a significant pH drop.
  • Respiration Effect: Remember, all living organisms in the tank, including fish and bacteria, release CO2 constantly, contributing to its accumulation if not well-balanced.

What Can Cause the pH Level to Rise?

On the flip side, if you find that the pH levels in your Angelfish tank are too high, it’s likely because of one of the following reasons:

1. Elevated Carbonate Hardness (KH)

Carbonate hardness, or KH, refers to the concentration of carbonate and bicarbonate ions in the water.

A higher KH generally leads to a more stable, and potentially higher, pH level in the aquarium.

  • Buffering Ability: Elevated KH acts as a buffer, preventing rapid pH swings and often pushing pH to the alkaline side.
  • Water Sources: Groundwater, especially from limestone regions, can have high carbonate levels, raising the KH and pH when used in aquariums.
  • Dissolving Shells: Some hobbyists use crushed coral or shells as substrate; these release carbonates, thus elevating both KH and pH.

2. Lack of Sufficient Carbon Dioxide (CO2)

While excess CO2 can drop pH, a deficiency can lead to a rise. Photosynthetic plants and effective aeration can reduce CO2, elevating pH.

  • Plant Photosynthesis: During daylight, aquatic plants consume CO2, which can cause a significant reduction in its levels, leading to a pH rise.
  • Efficient Aeration: Strong water agitation increases gas exchange, allowing CO2 to escape more easily and causing a pH increase.
  • Low Bioload: If a tank has few fish or organic elements producing CO2, the naturally lower CO2 levels can push pH up.

3. Overuse of Alkaline Materials

Intentionally or accidentally introducing alkaline substances can rapidly increase pH, potentially stressing aquatic life.

  • Baking Soda: A common pH adjuster, if used excessively, it can spike the pH beyond safe levels for aquatic inhabitants.
  • Decorative Rocks: Some rocks, like limestone or Texas Holey Rock, can slowly release minerals into the water, raising pH.
  • Commercial pH Up Products: While designed to raise pH, using them without monitoring or in excessive amounts can push pH to harmful levels.

4. Poor Filtration System

A well-functioning filtration system is essential for maintaining a stable aquarium environment.

If the filtration is inadequate, it might not remove waste products efficiently, which can indirectly lead to a rise in pH.

  • Ammonia Spikes: Inefficient filtration can allow ammonia from waste to accumulate; as bacteria convert it, they can consume hydrogen ions, raising pH.
  • Reduced Organic Breakdown: Proper filters help break down organic matter. Without this, some compounds might degrade in ways that elevate pH.
  • Lack of Beneficial Bacteria: Good filters support bacterial colonies. Without them, certain biochemical processes can shift, potentially affecting pH.

5. Infrequent Water Changes

Regular water changes help maintain a balanced and stable aquarium. Infrequent changes can allow certain minerals and compounds to concentrate, affecting the pH.

  • Mineral Concentration: Over time, tap water additives and minerals can concentrate if not diluted by water changes, leading to increased pH.
  • Evaporation Effects: As water evaporates, it leaves minerals behind, increasing the concentration of substances that might boost pH.
  • Reduced Toxin Dilution: Regular water changes help dilute toxins. Without them, certain byproducts might interact and cause a pH shift upwards.

How To Increase the pH Level In Your Aquarium?

To increase the pH level in your aquarium, you’ll need to introduce alkaline substances or minimize the acid-producing elements.

Boosting pH can help certain fish and plants preferring more alkaline environments.

  • Baking Soda: Dissolve 1 teaspoon per 5 gallons in tank water first; gradually add to tank while monitoring pH levels.
  • Crushed Coral or Limestone: Place a small bag in your filter or mix with substrate; their calcium carbonate content gradually elevates pH. My recommendation: 12PK Oolitic Limestone (link to Amazon).
  • Water Changes: Replace 10-20% of tank water with water of a higher pH, once or twice a week, observing the pH shifts.
  • Aerate More: Using an additional air stone or pump boosts oxygen, reducing CO2 and consequently raising pH levels. My recommendation: Hygger Aquarium Air Stone (link to Amazon).

How To Decrease the pH Level In Your Aquarium?

To decrease the pH level in your aquarium, incorporate acidifying agents or elements that consume excess minerals.

Reducing pH benefits species that favor more acidic surroundings.

  • Peat Moss: Insert a bag of peat moss in your filter; its tannic and humic acids naturally soften and acidify water.
  • Driftwood: Incorporate a piece into your tank; as it releases tannins over time, the pH slowly drops, also tinting water slightly. My recommendation: Dr. Moss Malaysian Driftwood (link to Amazon).
  • Rain or RO Water: Mix with tank water during changes; both have a naturally lower pH and help in gradual reduction.
  • Commercial pH Adjusters: Purchase from pet stores, but always dose according to instructions, testing pH frequently during use. For Angelfish, I would use the API PROPER pH 7.0 (link to Amazon).

Are Angelfish Sensitive to pH?

Yes, angelfish are sensitive to pH. These tropical fish, hailing from the Amazon, have evolved in specific water conditions and drastic pH changes can stress or harm them.

  • Natural Habitat: In the Amazon, angelfish often inhabit waters with a pH of 6.0 to 7.8, making them attuned to this range.
  • Sudden Changes: Rapid pH shifts, even within their comfort range, can stress angelfish, leading to health issues or reduced lifespan.
  • Breeding Concerns: For angelfish breeders, maintaining a stable pH is crucial, as variations can impact egg health and fry survival.

Does Low pH Affect Angelfish?

Yes, low pH can affect angelfish. While they can tolerate mildly acidic water, a pH level that’s too low can have negative effects on their health and behavior.

  • Metabolic Impact: Extremely acidic water can alter an angelfish’s metabolic processes, leading to health complications or lethargy.
  • Skin and Scale Issues: A pH that’s too low can irritate or damage their skin and scales, making them more prone to diseases.
  • Breeding Challenges: Acidic water can hinder successful breeding, potentially affecting egg fertilization or fry development.

Can Angelfish Handle High pH?

No, angelfish aren’t well-suited to prolonged high pH levels.

While they can temporarily tolerate conditions outside their natural range, consistently alkaline water can stress them and compromise their health.

  • Altered Physiology: In a high pH environment, angelfish might experience internal physiological changes, impacting their overall health and behavior.
  • Reduced Immunity: Prolonged exposure to high pH can weaken their immune system, making them susceptible to illnesses and infections.
  • Behavioral Indicators: If angelfish become lethargic, lose their appetite, or exhibit erratic swimming, it might indicate distress from an elevated pH level.

Additional Water Requirements for Angelfish

In addition to water pH, two other essential factors to take into account for Angelfish care are water hardness and temperature:

1. Temperature

Angelfish are tropical creatures, and thus, they require warm water to thrive. Maintaining the correct temperature is essential for their metabolism, growth, and overall well-being.

  • Ideal Range: Angelfish typically thrive in temperatures between 78°F to 84°F (25°C to 29°C), ensuring they remain active and healthy.
  • Consistency Matters: Temperature fluctuations can stress angelfish, so using a reliable heater and regularly checking with a thermometer is crucial.
  • Impact on Metabolism: Proper temperature ensures optimal metabolic rates; too cold, and their metabolism slows, impacting growth and health.

Also Read: Angelfish Temperature Guide

2. Water Hardness

While angelfish can tolerate a range of water hardness, they have a preference based on their native Amazonian habitats. Hardness can affect their skin, scales, and overall physiological health.

  • Natural Preference: In the wild, angelfish inhabit soft to moderately hard water, with a general hardness (GH) of 3 to 10 dH.
  • Scale Sensitivity: Extremely hard water can affect the angelfish’s delicate scales and slime coat, potentially leading to health issues.
  • Breeding Considerations: For those looking to breed, softer water is typically preferred, as it can improve breeding success and fry survival rates.

Also Read: Do Angelfish Like Hard Or Soft Water?


For those of you who are just skimming through, here’s a short summary:

  • Angelfish thrive best in a pH range of 6.8 to 7.8, with natural habitats in the Amazon River Basin having pH levels between 6.5 and 7.5.
  • Factors affecting pH drop in aquariums include natural biological activities, type of aquarium substrate, presence of tannins, low-pH tap water, and CO2 buildup.
  • Causes for pH rise include elevated carbonate hardness (KH), reduced CO2, use of alkaline materials, poor filtration systems, and infrequent water changes.
  • Angelfish are sensitive to pH changes; both extremely low and high pH levels can have adverse effects on their health, metabolism, and breeding success.
  • Besides pH, angelfish require specific water temperature (78°F to 84°F) and prefer soft to moderately hard water (GH of 3 to 10 dH) for optimal health and breeding.