Red Sea NO3:PO4-X 1L
Pack size
500 mL, 1 L and 5 L
Cost per litre
Under 1c
Water type
Saltwater + Reef
Red Sea NO3:PO4-X 1L
The size most established reef tanks settle on. Red Sea NO3:PO4-X is a liquid carbon source that feeds the bacteria already living in your reef system, encouraging them to consume excess nitrate and phosphate straight out of the water column. This 1 L bottle is the standard size once you're past the trial phase — enough for several months of daily dosing on a typical mixed reef, at a lower cost per litre than the 500 mL starter bottle.
Key features
- Feeds your own bacteria — a blend of carbon sources, each favoured by a different naturally occurring bacterial strain, so nutrient reduction happens biologically rather than through media that needs replacing.
- Treats nitrate and phosphate together — one bottle addresses both nutrients that drive nuisance algae, instead of running separate products for each.
- Cheaper per litre than the 500 mL bottle — the 1 L size stretches roughly twice as far for less than double the price.
- Dosed by an exact chart, not guesswork — Red Sea publishes a daily dose in millilitres per 100 L, set by your current nitrate and phosphate reading.
- Room-temperature storage — no refrigeration required; keep out of direct light.
Specifications
| Spec | Red Sea NO3:PO4-X 1 L |
|---|---|
| Volume | 1,000 mL |
| Form | Liquid concentrate, dosed daily |
| Water type | Marine / reef |
| Litres treated at the conservative dosing rate | Approx. 33,300 L over the life of the bottle |
| Cost per litre of water treated | Under 1c per litre |
Dosing chart — Red Sea's published rates
Dose is set by your current nitrate and phosphate readings, not a flat daily amount. Test weekly while dosing and adjust as levels fall.
| Parameter | Current level | Daily dose |
|---|---|---|
| Phosphate (PO₄) | Below 0.04 ppm | 1 mL per 100 L |
| Phosphate (PO₄) | 0.04–0.2 ppm | 2 mL per 100 L |
| Phosphate (PO₄) | Above 0.2 ppm | 3 mL per 100 L |
| Nitrate (NO₃) | Below 1 ppm | 1 mL per 100 L |
| Nitrate (NO₃) | Above 1 ppm | 2 mL per 100 L |
Where both nutrients are elevated at once, follow Red Sea's full instructions on combining the two doses rather than simply adding them together.
Which size do I need?
For a tank around 200–400 L dosed daily, a 1 L bottle typically covers several months even at the top dosing rate — long enough to see whether the product is bringing your nutrients under control before restocking.
| Size | Price | Approx. litres treated* | Cost per litre |
|---|---|---|---|
| 500 mL | $27.00 | ~16,650 L | Under 1c per litre |
| 1 L (this bottle) | $42.00 | ~33,300 L | Under 1c per litre |
| 5 L | $157.00 | ~166,650 L | Under 1c per litre |
*Calculated at Red Sea's top published dosing rate of 3 mL per 100 L per day — the conservative, lowest-yield case, used when phosphate reads above 0.2 ppm. At lower nutrient levels the same bottle treats considerably more water and lasts longer.
Suitable for, and not suitable for
- Suitable for established marine and reef aquariums running an efficient protein skimmer.
- Suitable for use alongside Red Sea's Algae Management program when converting a tank off phosphate- and nitrate-absorbing media.
- Not suitable for use at the same time as sulphur-based denitrators.
- Not a spot treatment — this product doses the whole system daily, not a single application.
Dosage and directions
Add daily to the sump, or to a high-flow area of the display if there's no sump — never dosed directly onto coral. A dosing pump is worth setting up at this bottle size, since the daily volume needs to stay consistent over months, not days.
Care and maintenance
Test nitrate and phosphate weekly while dosing and adjust to the chart above. Keep the protein skimmer running efficiently — the bacteria this product feeds are exported largely through skimmate, so a skimmer sized to your system matters as much as the dose itself.
Safety
Reduce the dose by half if nitrate falls below 0.25 ppm, and don't increase the dose faster than the chart allows — overdosing a carbon source can crash dissolved oxygen. Red Sea recommends switching off any UV steriliser while dosing, since UV will kill the bacteria the product is feeding. Not for use in planted or shrimp-only systems.
Goes well with
- Red Sea Nutrients Control Multi Test Kit (NO3/PO4) — the weekly nitrate and phosphate test this dosing chart is based on.
- Red Sea Reefer Skimmer 300 — efficient skimming is what exports the nutrient-laden bacteria this product feeds.
Warranty and delivery
Backed by Red Sea's standard product warranty, in addition to your rights under Australian Consumer Law. A 1 L bottle ships as a standard parcel.
Common questions
How much cheaper is the 1 L bottle than buying two 500 mL bottles?
At $42.00 for 1 L versus $54.00 for two 500 mL bottles ($27.00 each), the 1 L bottle is roughly 22% cheaper for the same volume.
How long will a 1 L bottle last?
At Red Sea's top dosing rate it treats roughly 33,300 L of tank water — for a 300 L system dosed daily at the highest rate, that's a little over three and a half months. Most tanks use less than the top rate, so a bottle typically lasts longer.
Can I use NO3:PO4-X alongside GFO or nitrate-removing media?
Yes — Red Sea's Algae Management program is built around gradually removing absorption media while introducing this product. Follow Red Sea's published conversion schedule rather than removing media all at once.
Will this cloud my water or affect coral colour?
Dosed at the correct rate it shouldn't cloud the water. As nitrate and phosphate come down, many reef keepers see coral colouration improve, though results depend on your system's starting point and lighting.
