Will biopellets crash my nitrate to zero?

Possibly, if you load aggressively. Below 0.5 ppm NO₃ risks dinoflagellate outbreaks. Aim for 5–10 ppm NO₃ and 0.03–0.08 ppm PO₄ as targets — biopellets pulling either below that point is over-dosed.

Can I use biopellets with GFO or vinegar dosing?

Yes, but watch parameters closely. Biopellets + GFO can crash PO₄ fast; biopellets + vinegar doubles carbon-source impact. Start one at a time, stabilise, then layer the second.

How long do biopellets last?

6–12 months in normal use. They visibly shrink as they're consumed. Refill the reactor as the volume drops to ~50 % of initial. Replace fully when the polymer becomes brittle or off-coloured.

Calculator

Biopellet Dose Calculator (NP-Reducing Polymer)

Name: Biopellet Dose Calculator (NP-Reducing Polymer)
Author: reefcalcs

Biopellets (Vertex N/P-Reducing, Two Little Fishies NPX, generic polymer) are slow-release carbon sources tumbled in a fluidised reactor. Bacteria consume the carbon and the nitrate / phosphate alongside it. Get the loading right and NO₃/PO₄ both drop into target range; overshoot and you spike a bacterial bloom that kills coral.

JavaScript is disabled in your browser, so the interactive calculator below won't run. The math, formula, and worked example are all written out further down this page under “How this is calculated.” Enable JS (or open this page in another browser) to use the live calculator.

Whether you compute by hand or in the calculator, the same caveat applies: verify against your test kit and the linked primary source before dosing. reefcalcs is reference information, not veterinary or engineering advice.

Biopellet dose

Tank volume (US gal)

Start standard; bump to aggressive only if NO₃/PO₄ won't budge.

Pellets needed (target volume)

375mL

Reactor flow (min)

113GPH

Reactor flow (max)

225GPH

1-2 grains/sec tumble.

Ramp-up schedule

Week	Active volume
Week 1	94 mL
Week 2	188 mL
Week 3	281 mL
Week 4	375 mL

Standard dose: 500 mL pellets per ~100 gal (Vertex Biopellet chart). Tumble in fluidised reactor; ramp up over 4 weeks to avoid bacterial bloom.

How this is calculated

Loading rates (mL biopellets per gallon):
  Conservative  3.3   (low-nutrient tanks)
  Standard      5.0   (default)
  Aggressive    10.0  (high NO₃/PO₄)

Initial dose = tank_gal × loading_mL_per_gal

Ramp-up schedule (avoid bacterial bloom):
  Week 1: 25 % of target volume
  Week 2: 50 %
  Week 3: 75 %
  Week 4: 100 %

Reactor flow:
  GPH = (target_mL / 500) × 150–300
  Tumble pellets at 1–2 grains/sec.

Standard dose (500 mL per ~100 gal) is the Vertex Biopellet chart starting point. The 4-week ramp is critical — going from 0 to full overnight stages a population explosion of carbon-fed bacteria that consume O₂ and shed cloudy water. Add the carbon source slowly, test NO₃/PO₄ weekly.

FAQ

Will biopellets crash my nitrate to zero?: Possibly, if you load aggressively. Below 0.5 ppm NO₃ risks dinoflagellate outbreaks. Aim for 5–10 ppm NO₃ and 0.03–0.08 ppm PO₄ as targets — biopellets pulling either below that point is over-dosed.
Can I use biopellets with GFO or vinegar dosing?: Yes, but watch parameters closely. Biopellets + GFO can crash PO₄ fast; biopellets + vinegar doubles carbon-source impact. Start one at a time, stabilise, then layer the second.
How long do biopellets last?: 6–12 months in normal use. They visibly shrink as they're consumed. Refill the reactor as the volume drops to ~50 % of initial. Replace fully when the polymer becomes brittle or off-coloured.

Share / embed this calculator

Paste this snippet into any blog or forum post that allows raw HTML to embed the calculator.

<iframe
  src="https://reefcalcs.com/embed/biopellet-dose/"
  width="100%"
  height="720"
  style="border: 1px solid #1C2D34; border-radius: 8px; max-width: 720px;"
  loading="lazy"
  title="ReefCalcs Biopellet Dose Calculator (NP-Reducing Polymer)"
></iframe>

Sources & references

01
Vertex — biopellet product info + dosing chart
https://www.bulkreefsupply.com/vertex-biopellets-pro-bio-pellets.html
02
BRS — biopellet guide
https://www.bulkreefsupply.com/content/post/biopellets-a-complete-guide
03
Two Little Fishies — NPX biopellets
https://www.twolittlefishies.com/products/biopellets-npx-bioplastics

Last reviewed 2026-05-25