𝐓𝐡𝐞 𝐃𝐚𝐧𝐠𝐞𝐫 𝐨𝐟 𝐙𝐞𝐫𝐨 𝐍𝐢𝐭𝐫𝐚𝐭𝐞𝐬 𝐚𝐧𝐝 𝐏𝐡𝐨𝐬𝐩𝐡𝐚𝐭𝐞𝐬 𝐢𝐧 𝐑𝐞𝐞𝐟 𝐓𝐚𝐧𝐤𝐬

𝐓𝐡𝐞 𝐃𝐚𝐧𝐠𝐞𝐫 𝐨𝐟 𝐙𝐞𝐫𝐨 𝐍𝐢𝐭𝐫𝐚𝐭𝐞𝐬 𝐚𝐧𝐝 𝐏𝐡𝐨𝐬𝐩𝐡𝐚𝐭𝐞𝐬 𝐢𝐧 𝐑𝐞𝐞𝐟 𝐓𝐚𝐧𝐤𝐬

Introduction

In a reef tank, it's essential to maintain proper levels of nitrates and phosphates because these nutrients are vital to coral health. While it's important to keep these levels low, bringing them down to zero can be harmful, especially for certain types of corals. Corals require a balanced amount of nutrients for growth, color, and general well-being. When levels drop too low, corals can lose color, stop growing, or even die.

The Role of Nitrates and Phosphates

• • Nitrates (NO₃) and phosphates (PO₄) are necessary nutrients for coral growth, but in excess, they can lead to problems like algal blooms and reduced water quality.

  • Zero nitrates and phosphates are dangerous because corals rely on small amounts of these nutrients for photosynthesis and tissue growth. A completely nutrient-poor environment can starve the corals and cause their zooxanthellae (the symbiotic algae that live in their tissues and help them produce energy) to die off, leading to bleaching.

Why Nutrients Shouldn't Reach Zero

• • Bacterial Imbalance: When nutrient levels drop too low, the bacteria in the tank might consume all available resources, leading to a nutrient-deprived system.

  • Coral Starvation: Corals depend on the nutrients from both the water column and their zooxanthellae. If the tank is stripped of nitrates and phosphates, corals may not get enough nutrients for metabolic processes.

  • Loss of Color (Pale Corals): A lack of nutrients leads to coral tissue thinning and loss of vibrancy, often called "paling." Corals may appear washed out or bleached due to the absence of nutrients required by their symbiotic algae.

Optimal Nitrate and Phosphate Levels by Coral Type

Different types of corals have varying nutrient requirements, and maintaining specific nitrate and phosphate levels helps support their health and coloration. Below is a breakdown of nutrient needs for SPS (Small Polyp Stony), LPS (Large Polyp Stony), and soft corals:

SPS Corals (e.g., Acropora, Montipora)

• • Nitrate Range: 1-5 ppm

  • Phosphate Range: 0.01-0.05 ppm

  • Why: SPS corals thrive in low-nutrient environments because they come from areas of the reef with clear, nutrient-poor waters. However, they still need some nitrates and phosphates for proper growth and pigmentation. If these levels fall to zero, SPS corals can lose color and health quickly.

LPS Corals (e.g., Acanthophyllia, Euphyllia)

• • Nitrate Range: 2-10 ppm

  • Phosphate Range: 0.03-0.1 ppm

  • Why: LPS corals tolerate slightly higher nutrient levels than SPS corals and can benefit from this, particularly in terms of growth and expansion. They typically come from more turbid waters with slightly higher nutrient availability. However, excessively high levels can still promote algal growth and smother the corals.

Soft Corals (e.g., Xenia, Zoanthids)

• • Nitrate Range: 5-20 ppm

  • Phosphate Range: 0.03-0.2 ppm

  • Why: Soft corals are more tolerant of higher nutrient levels than SPS and LPS corals. They often thrive in nutrient-rich environments and can even benefit from moderately higher nitrate and phosphate levels. These corals can withstand higher nutrient levels without showing stress, making them more resilient to fluctuating water conditions.

Balancing Nutrient Levels in Your Tank

Maintaining a balanced environment is key to coral health. Here are some guidelines to help keep nitrate and phosphate levels in check:

• • Regular Testing: Test your water regularly to monitor nitrate and phosphate levels. Adjust dosing (like carbon dosing) or nutrient export methods (protein skimmers, refugiums) based on test results.

  • Controlled Feeding: Overfeeding can increase nitrate and phosphate levels, so feed sparingly and ensure that food is consumed quickly.

  • Carbon Dosing: If you're using carbon dosing (vodka, vinegar, or sugar), be cautious not to strip the tank of all nutrients. Carbon dosing can lower nitrates and phosphates, but dosages must be fine-tuned to maintain appropriate levels for coral health.

Help! My levels are too low

If your tank's nitrate (NO3) and phosphate (PO4) levels reach zero, it can lead to several potential problems, especially for coral health, including "nutrient starvation." Corals, especially certain types like soft corals and some LPS (Large Polyp Stony) corals, rely on small amounts of nutrients to thrive. Here’s what you can do if you find yourself in this situation:

1. Test Water Parameters

• • Double-check the measurements using accurate and calibrated test kits to ensure nitrate and phosphate levels are indeed at zero.
  • Assess other parameters like alkalinity, calcium, and magnesium to see if imbalances could be causing coral stress.

2. Reduce Carbon Dosing

• • If you are carbon dosing (e.g., vinegar, vodka, or biopellets), immediately reduce or pause the dosing. Carbon dosing enhances bacterial growth, which consumes nitrate and phosphate. Cutting back will allow nutrient levels to stabilize.

3. Feed More Heavily

• • Increase fish feeding slightly to add more waste and organic matter, which can raise nitrate and phosphate levels.
  • Consider coral target feeding with reef-safe foods such as reef roids, phytoplankton, or other coral nutrition supplements to help increase nutrients naturally.

4. Add Nutrients Carefully

• • Direct supplementation of nitrate (e.g., sodium nitrate) or phosphate (e.g., sodium phosphate) may be necessary in cases of persistently low levels. However, dosing must be done carefully and gradually to avoid spikes.
  • Products like NeoNitro and NeoPhos from Brightwell Aquatics are available to raise nitrates and phosphates safely.

5. Adjust Protein Skimming

• • Turn off or dial back your protein skimmer temporarily to allow more organic material to remain in the system, which can naturally increase nutrient levels.

6. Refugium and Macroalgae Control

• • If you are running a refugium with macroalgae (such as Chaetomorpha), consider trimming or removing some of the algae. Macroalgae can rapidly consume nitrates and phosphates, so reducing its biomass can help nutrient levels rise again.

7. Avoid Large Water Changes

• • While water changes are helpful for reducing excess nutrients, if your levels are already at zero, performing large water changes can dilute what little remains. Smaller, less frequent water changes can prevent nutrient levels from further dropping.

8. Monitor Coral Health

• • Corals, especially SPS (Small Polyp Stony) corals, can bleach or lose color when deprived of essential nutrients. Keep an eye on your corals and look for any signs of stress, such as reduced polyp extension, pale colors, or tissue loss.

9. Gradual Increase of Nutrients

• • Aim for small, gradual changes when adjusting nitrate and phosphate levels. Too rapid an increase could lead to algae blooms, bacterial blooms, or an imbalance that may stress corals and fish.

Conclusion

Maintaining the right balance of nutrients is essential for coral health in a saltwater tank. While high nitrate and phosphate levels can lead to algae growth and water quality issues, levels that are too low can starve corals, causing them to lose color and potentially die. Different coral types require specific ranges of nutrients, so it's important to tailor your nutrient management practices based on the types of corals you keep.

Happy Reefing!