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My Tank Thread
Raising nutrients isn’t always easy; for some systems, it can feel like an uphill battle: confusing, frustrating, and full of contradictory advice. It’s not always clear which products to use, what to dose, or which filtration methods to adjust or remove.
Chronically low nutrients are increasingly believed to play a role in coral bleaching, pale colors, tissue necrosis, polyp bailout, and severely stunted growth. Even worse, low phosphate levels are well known to encourage toxic dinoflagellates, which can stress and even outright kill invertebrates and corals. Finally, keeping nutrients detectable offers peace of mind by removing starvation as a variable and simplifying future problem-solving.
1. Reduce Excess Filtration
If nutrients are chronically undetectable, certain filtration methods can be paused or reduced; however, not all systems are designed purely for nutrient removal. Some forms of filtration also play essential roles in oxygenation, pH stability, and overall reef health, and removing them entirely can be counterproductive.
Figure 1: @VintageReefer's very lush turf algae in a Santa Monica Surf 2 scrubber has benefits beyond nutrient control
Here’s a breakdown of what’s safe to adjust, and what’s better left in place:
Protein Skimmers
Skimmers should generally remain running. They are not effective at removing nitrate or phosphate directly, and they serve important functions such as removing organics, bacteria, heavy metals, and CO₂, while also supporting oxygen saturation. Removing the skimmer is rarely beneficial and may cause more harm than good.
Bacterial Export (Carbon Dosing, Biopellets, Denitrators)
Bacterial-based filtration methods are highly effective at reducing nutrients, particularly nitrate. If your tank is already running low, it’s often best to reduce or pause these approaches until levels increase. Some modern products, like NP Bacto Balance, include some nutrients in their formulation to help prevent nutrient depletion: a promising compromise in certain systems. Nevertheless, scaling back the dosage is a safe and flexible option when nutrients are trending too low.
Refugiums
Algae-based filtration can be scaled back if desired, but completely removing them is usually not required. A shortened photoperiod is a gentler alternative to reduce export while preserving the pH and oxygen benefits refugiums offer, not to mention the habitat they provide for zooplankton.
Water Changes
You can reduce their frequency or volume, but there’s no need to avoid them completely. Water changes offer benefits beyond nutrient control, and no other method removes organics as effectively. They don’t just dilute: they realign. If an element is too low, the new water brings it up. If it’s too high, the water change brings it down. Over time, this pulls parameters toward the baseline of your salt mix.
Mechanical Filtration (Filter Socks, Floss, Roller Mats)
These have minimal effect on dissolved nutrients and don’t need to be removed. You can keep them for water clarity and detritus control.
Chemical Media (Activated Carbon, Purigen)
These do not significantly affect nitrate or phosphate levels and can remain in the system. Their benefits lie more in water clarity and the removal of organic discoloration or toxins.
Phosphate Removers (GFO, PhosGuard, etc.)
If phosphate is already undetectable or bottomed out, remove these immediately. Continuing to run phosphate adsorbers can starve corals and increase the risk of dinoflagellate outbreaks.
Other Media (Matrix, Bio Bricks, Zeolites)
These have little to no direct impact on nutrient levels and can be left in place without issue.
2. Feeding More to Raise Both Nitrate and Phosphate
If both nitrate and phosphate are low, increasing feeding is a natural first step.
Feeding reliably raises both nutrients. However, if the tank’s uptake is extraordinarily high, it may take time and require more than just maintenance-level feeding before you see measurable results.
Figure 2: @vetteguy53081 has an arsenal of frozen foods for his fish
We have a wide array of nutrient-rich foods available:
3. Foods with Nutrient Biases
Some foods have an imbalanced nitrate-to-phosphate ratio, which can be useful if one nutrient is disproportionately low.
Figure 3: Strawberry Shortcake Acropora by @Big E. He usually maintains detectable nutrients in his aquariums with feedings.
Reef Roids is often used as a phosphate source. It contains both nitrogen and phosphorus, but with a strong phosphate bias.
Amino acids, on the other hand, only provide nitrogen, making them helpful if only nitrate is limiting. While amino acids can support coral coloration and polyp extension, they must be used sparingly. Though they contain nitrogen, they also include organic carbon, which may stimulate bacterial growth. In some cases, this can lead to increased biofilms or cloudy water, especially when dosed heavily. Their impact on nitrate levels is inconsistent and may vary by system. Avoid entirely if dinoflagellates are present, as they may exasperate blooms.
4. Targeted Nutrient Dosing for Nitrate or Phosphate
Sometimes the nutrient demand is so high that food alone won’t raise your levels quickly enough without creating pollution. That’s when chemical dosing becomes the cleanest and most controllable method. It quickly raises nutrients without overloading the tank with organics or waste, and allows precision control.
Figure 4: My trachyplyllia and acanthophyllia corals are the first to suffer when nutrients are too low
When nutrients are too low, I prefer to use targeted dosing to bring nutrients into a more optimal range, then maintain it with feedings. Some tanks may benefit from automated nutrient dosing, either through a dosing pump or integrated into the top-off system, which can be very convenient if it has an especially high nutrient-demand.
Important: Use High-Purity Chemicals
Skip "stump remover" or hobby blends with unknown impurities. Food-grade compounds are cheaper, widely available, and very pure.
5. Nitrate Dosing
I recommend sodium nitrate (NaNO₃) over potassium nitrate, as the latter may cause excessive potassium buildup. There’s no universal target for nitrate. Some reefers prefer lower levels, while others maintain higher ranges. Unlike phosphate, nitrate isn’t heavily bound by rocks, so it responds more predictably to dosing. It’s best to increase levels gradually and monitor how your tank responds, adjusting as needed based on your system’s needs.
Sodium Nitrate (NaNO₃) Recipe:
Sodium nitrate is 72.95% nitrate (NO₃⁻) by weight.
1 ppm in 100 L = 100 mg of nitrate.
100 ÷ 0.7295 = 137.1 mg of sodium nitrate.
To make a stock solution where 1 mL = 1 ppm in 100 L:
Dissolve 137.1 g of NaNO₃ in 1 L of freshwater.
Dose 1 mL per 100 L to raise NO₃ by 1 ppm.
Here’s my latest nitrate dosing DIY thread that uses the same recipe as this article:
www.reef2reef.com
6. Using Ammonium as a Direct Nitrogen Source
Ammonium is the preferred nitrogen source for photosynthetic organisms, and many corals respond better to it than nitrate.
Ammonium is rapidly converted to nitrate in tanks with healthy biofilters, but it offers a more direct nitrogen supply. Most ammonia tests aren’t accurate enough for established tanks, but we can monitor nitrate levels to adjust the ammonium dose:
Dissolve 20 grams of ammonium bicarbonate in 1 L of freshwater.
To add 0.1 mg/L (equivalent to 0.36 ppm nitrate) ammonia to an aquarium, dose 2.3 mL of this solution per 100 L (26 gallons). Depending on demand, it may need to be added multiple times per day to maintain or increase nitrate levels.
Here's the full thread and guide on how to safely add Ammonium to a reef tank by @Randy Holmes-Farley
www.reef2reef.com
7. Phosphate Dosing
If phosphate is flatlined, corals are stressed, and dinoflagellates are beginning to creep in, start with a full 0.15 ppm dose, not less.
Don’t tiptoe. Rocks and sand bind phosphate aggressively. Small daily doses often get adsorbed immediately and fail to raise water levels meaningfully. Testing daily, only to watch levels crash back to zero, is tedious and wastes time and reagents. A strong initial dose helps establish equilibrium faster and gives your tank breathing room. You can continue dosing phosphate as needed or supplement with additional feedings. If dinoflagellates are a concern, ensure phosphate remains consistently above 0.10 ppm.
Sodium Phosphate Dibasic (Na₂HPO₄) Recipe:
Sodium phosphate dibasic (Na₂HPO₄) is 66.9% phosphate (PO₄³⁻) by weight.
0.02 ppm in 100 L = 2 mg of PO₄³⁻.
2 ÷ 0.669 = 2.99 mg of Na₂HPO₄.
To make a stock solution where 1 mL = 0.02 ppm in 100 L:
Dissolve 3 g of Sodium phosphate dibasic (Na₂HPO₄) in 1 L of freshwater.
Dose 1 mL per 100 L to raise PO₄ by 0.02 ppm.
Note: Monobasic, dibasic, and tribasic forms are interchangeable. Concentrations vary slightly but are functionally similar when accounting for rock adsorption.
Here’s my latest phosphate dosing DIY thread that uses the same recipe as this article:
www.reef2reef.com
Quick Reference Dosing Chart:
For convenience, here’s a breakdown of the recipes and their corresponding nutrient increases.
You can use this calculator if that’s easier: http://www.theplantedtank.co.uk/calculator.htm
Select potassium nitrate or potassium phosphate. The result is close enough.
Final Thoughts
It’s time to raise nutrients when your test kits are flashing low numbers and your tank is sending warning signs: pale colors, retracted polyps, declining health, and the early stages of dinoflagellate growth. Addressing the issue early is key.
Reducing filtration exports less. Feeding adds natural prey and beneficial organics, when done in moderation. Chemical dosing gives you precision, purity, and speed. Either method can help get nutrients back up to increase coral growth and color, and also reduce pest dinos.
Chronically low nutrients are increasingly believed to play a role in coral bleaching, pale colors, tissue necrosis, polyp bailout, and severely stunted growth. Even worse, low phosphate levels are well known to encourage toxic dinoflagellates, which can stress and even outright kill invertebrates and corals. Finally, keeping nutrients detectable offers peace of mind by removing starvation as a variable and simplifying future problem-solving.
1. Reduce Excess Filtration
If nutrients are chronically undetectable, certain filtration methods can be paused or reduced; however, not all systems are designed purely for nutrient removal. Some forms of filtration also play essential roles in oxygenation, pH stability, and overall reef health, and removing them entirely can be counterproductive.
Figure 1: @VintageReefer's very lush turf algae in a Santa Monica Surf 2 scrubber has benefits beyond nutrient control
Here’s a breakdown of what’s safe to adjust, and what’s better left in place:
Protein Skimmers
Skimmers should generally remain running. They are not effective at removing nitrate or phosphate directly, and they serve important functions such as removing organics, bacteria, heavy metals, and CO₂, while also supporting oxygen saturation. Removing the skimmer is rarely beneficial and may cause more harm than good.
Bacterial Export (Carbon Dosing, Biopellets, Denitrators)
Bacterial-based filtration methods are highly effective at reducing nutrients, particularly nitrate. If your tank is already running low, it’s often best to reduce or pause these approaches until levels increase. Some modern products, like NP Bacto Balance, include some nutrients in their formulation to help prevent nutrient depletion: a promising compromise in certain systems. Nevertheless, scaling back the dosage is a safe and flexible option when nutrients are trending too low.
Refugiums
Algae-based filtration can be scaled back if desired, but completely removing them is usually not required. A shortened photoperiod is a gentler alternative to reduce export while preserving the pH and oxygen benefits refugiums offer, not to mention the habitat they provide for zooplankton.
Water Changes
You can reduce their frequency or volume, but there’s no need to avoid them completely. Water changes offer benefits beyond nutrient control, and no other method removes organics as effectively. They don’t just dilute: they realign. If an element is too low, the new water brings it up. If it’s too high, the water change brings it down. Over time, this pulls parameters toward the baseline of your salt mix.
Mechanical Filtration (Filter Socks, Floss, Roller Mats)
These have minimal effect on dissolved nutrients and don’t need to be removed. You can keep them for water clarity and detritus control.
Chemical Media (Activated Carbon, Purigen)
These do not significantly affect nitrate or phosphate levels and can remain in the system. Their benefits lie more in water clarity and the removal of organic discoloration or toxins.
Phosphate Removers (GFO, PhosGuard, etc.)
If phosphate is already undetectable or bottomed out, remove these immediately. Continuing to run phosphate adsorbers can starve corals and increase the risk of dinoflagellate outbreaks.
Other Media (Matrix, Bio Bricks, Zeolites)
These have little to no direct impact on nutrient levels and can be left in place without issue.
2. Feeding More to Raise Both Nitrate and Phosphate
If both nitrate and phosphate are low, increasing feeding is a natural first step.
Feeding reliably raises both nutrients. However, if the tank’s uptake is extraordinarily high, it may take time and require more than just maintenance-level feeding before you see measurable results.
Figure 2: @vetteguy53081 has an arsenal of frozen foods for his fish
We have a wide array of nutrient-rich foods available:
- Flakes
- Pellets
- Frozen foods
- Powdered coral foods (e.g., Reef Roids, Benepets, Reef Chili)
- Phytoplankton
- Liquid foods (e.g., R.O.E., Oyster Feast)
- Live foods
- Adds diversity to both fish and coral diets
- Encourages natural coral feeding behaviors
- Easy to implement. Some version of this is probably already in your freezer or cabinet
- If the tank size permits, you get to add more fish: a boost for nutrients and for the overall vibrancy of the tank
- Can increase organic waste, detritus, water yellowing, and tannins
- May worsen Aiptasia, cyanobacteria, or dinoflagellate issues
- May not act fast enough in dire situations
3. Foods with Nutrient Biases
Some foods have an imbalanced nitrate-to-phosphate ratio, which can be useful if one nutrient is disproportionately low.
Figure 3: Strawberry Shortcake Acropora by @Big E. He usually maintains detectable nutrients in his aquariums with feedings.
Reef Roids is often used as a phosphate source. It contains both nitrogen and phosphorus, but with a strong phosphate bias.
Amino acids, on the other hand, only provide nitrogen, making them helpful if only nitrate is limiting. While amino acids can support coral coloration and polyp extension, they must be used sparingly. Though they contain nitrogen, they also include organic carbon, which may stimulate bacterial growth. In some cases, this can lead to increased biofilms or cloudy water, especially when dosed heavily. Their impact on nitrate levels is inconsistent and may vary by system. Avoid entirely if dinoflagellates are present, as they may exasperate blooms.
4. Targeted Nutrient Dosing for Nitrate or Phosphate
Sometimes the nutrient demand is so high that food alone won’t raise your levels quickly enough without creating pollution. That’s when chemical dosing becomes the cleanest and most controllable method. It quickly raises nutrients without overloading the tank with organics or waste, and allows precision control.
Figure 4: My trachyplyllia and acanthophyllia corals are the first to suffer when nutrients are too low
When nutrients are too low, I prefer to use targeted dosing to bring nutrients into a more optimal range, then maintain it with feedings. Some tanks may benefit from automated nutrient dosing, either through a dosing pump or integrated into the top-off system, which can be very convenient if it has an especially high nutrient-demand.
Important: Use High-Purity Chemicals
Skip "stump remover" or hobby blends with unknown impurities. Food-grade compounds are cheaper, widely available, and very pure.
5. Nitrate Dosing
I recommend sodium nitrate (NaNO₃) over potassium nitrate, as the latter may cause excessive potassium buildup. There’s no universal target for nitrate. Some reefers prefer lower levels, while others maintain higher ranges. Unlike phosphate, nitrate isn’t heavily bound by rocks, so it responds more predictably to dosing. It’s best to increase levels gradually and monitor how your tank responds, adjusting as needed based on your system’s needs.
Sodium Nitrate (NaNO₃) Recipe:
Sodium nitrate is 72.95% nitrate (NO₃⁻) by weight.
1 ppm in 100 L = 100 mg of nitrate.
100 ÷ 0.7295 = 137.1 mg of sodium nitrate.
To make a stock solution where 1 mL = 1 ppm in 100 L:
Dissolve 137.1 g of NaNO₃ in 1 L of freshwater.
Dose 1 mL per 100 L to raise NO₃ by 1 ppm.
Here’s my latest nitrate dosing DIY thread that uses the same recipe as this article:
DIY Nitrate Dosing Recipe
Here’s a quick guide of the DIY nitrate recipes we commonly use for reef tanks. Sodium nitrate and calcium nitrate are the most common materials used. It’s crucial to ensure that these compounds are food-grade or have a purity rating. Sourcing pure chemicals is more economical than purchasing...
www.reef2reef.com
Ammonium is the preferred nitrogen source for photosynthetic organisms, and many corals respond better to it than nitrate.
Ammonium is rapidly converted to nitrate in tanks with healthy biofilters, but it offers a more direct nitrogen supply. Most ammonia tests aren’t accurate enough for established tanks, but we can monitor nitrate levels to adjust the ammonium dose:
- If nitrate rises steadily → ammonium is in a surplus.
- If nitrate declines steadily → ammonium is in a deficit and the dosage could be increased if desired.
Dissolve 20 grams of ammonium bicarbonate in 1 L of freshwater.
To add 0.1 mg/L (equivalent to 0.36 ppm nitrate) ammonia to an aquarium, dose 2.3 mL of this solution per 100 L (26 gallons). Depending on demand, it may need to be added multiple times per day to maintain or increase nitrate levels.
Here's the full thread and guide on how to safely add Ammonium to a reef tank by @Randy Holmes-Farley
DIY ammonia dosing for low N systems
See the thread here: https://www.reef2reef.com/threads/diy-ammonia-dosing-for-low-nitrate-systems.987087/
www.reef2reef.com
7. Phosphate Dosing
If phosphate is flatlined, corals are stressed, and dinoflagellates are beginning to creep in, start with a full 0.15 ppm dose, not less.
Don’t tiptoe. Rocks and sand bind phosphate aggressively. Small daily doses often get adsorbed immediately and fail to raise water levels meaningfully. Testing daily, only to watch levels crash back to zero, is tedious and wastes time and reagents. A strong initial dose helps establish equilibrium faster and gives your tank breathing room. You can continue dosing phosphate as needed or supplement with additional feedings. If dinoflagellates are a concern, ensure phosphate remains consistently above 0.10 ppm.
Sodium Phosphate Dibasic (Na₂HPO₄) Recipe:
Sodium phosphate dibasic (Na₂HPO₄) is 66.9% phosphate (PO₄³⁻) by weight.
0.02 ppm in 100 L = 2 mg of PO₄³⁻.
2 ÷ 0.669 = 2.99 mg of Na₂HPO₄.
To make a stock solution where 1 mL = 0.02 ppm in 100 L:
Dissolve 3 g of Sodium phosphate dibasic (Na₂HPO₄) in 1 L of freshwater.
Dose 1 mL per 100 L to raise PO₄ by 0.02 ppm.
Note: Monobasic, dibasic, and tribasic forms are interchangeable. Concentrations vary slightly but are functionally similar when accounting for rock adsorption.
Here’s my latest phosphate dosing DIY thread that uses the same recipe as this article:
DIY Phosphate Dosing Recipe
Sometimes phosphate can be so stubbornly low that the only way to meaningfully raise it is by directly dosing phosphate. When you feed foods, you’re adding nitrogen, carbon, and loads of organics. This effect is compounded if you’re trying to offset rocks that initially work against you by...
www.reef2reef.com
Quick Reference Dosing Chart:
For convenience, here’s a breakdown of the recipes and their corresponding nutrient increases.
Chemical: | Recipe: | Dose per 100 L: | Result: |
Sodium nitrate | 137.1 g/L | 1mL | +1 ppm NO3 |
Ammonium bicarbonate | 20 g/L | 2.3 mL | +0.1 ppm NH3 (0.36 ppm NO₃) |
Sodium phosphate dibasic | 3 g/L | 1mL | +0.02 ppm PO4 |
You can use this calculator if that’s easier: http://www.theplantedtank.co.uk/calculator.htm
Select potassium nitrate or potassium phosphate. The result is close enough.
Final Thoughts
It’s time to raise nutrients when your test kits are flashing low numbers and your tank is sending warning signs: pale colors, retracted polyps, declining health, and the early stages of dinoflagellate growth. Addressing the issue early is key.
Reducing filtration exports less. Feeding adds natural prey and beneficial organics, when done in moderation. Chemical dosing gives you precision, purity, and speed. Either method can help get nutrients back up to increase coral growth and color, and also reduce pest dinos.
Last edited:
Thanks for all your help all!
