FAULT ISOLATION MANUAL · NUTRIENTS — NITRATE

NO3-002 · Nitrate at zerov1.0.1

Nitrate reads at or below detection: undetectable, or repeatedly bottoming out. This sheet isolates why, the way an aircraft maintenance manual would: confirm the zero on a second method, cross the safety gates, then walk the export and input chain. Corrections restore nitrogen input or reduce export one measured step at a time: nothing is dosed from a bottle.

WHAT YOU'LL NEED

Your nitrate test kit plus a second method (different kit, low-range method, or your ICP result)
A phosphate test or low-range checker
Your carbon-dosing log, if you run a program
Your feeding and equipment records
Your tank journal

JavaScript is off, so the interactive sheet can't run — the complete printed logic is below. Start at block 1 and follow the YES/NO links. Nothing about your tank is inferred or stored.

Block 1 — Did your most recent properly performed nitrate test read at or below the kit's detection limit, effectively zero? (Note: Some methods report nitrate as nitrogen (NO₃-N), while this Manual uses nitrate as NO₃. Confirm the reporting basis before comparing results. NO₃ is approximately 4.43 times NO₃-N.)
YES → block 3 · NO → block 2

Block 2 — NO3-002 NOT ACTIVE — your nitrate is measurable. This sheet covers nitrate at or below detection: undetectable, or repeatedly bottoming out. If nitrate is above the applicable upper boundary for your tank type, return to the Manual index and use NO3-001 instead.
END — NO FAULT

Block 3 — Is the zero persistent: have at least two properly performed tests, spaced days apart, read at or below detection? A single zero can be a handling error or a temporary dip.
YES → block 5 · NO → block 4

Block 4 — One low reading is not a trend. Retest with careful technique over the next few days before changing anything: nitrate that is genuinely bottoming out will keep reading at or below detection. Run this procedure again once you have two comparable results spaced days apart.
END — ESCALATE RETEST

Block 5 — Confirm the zero with a second, appropriate method: a different brand of kit, a low-range method, or your ICP result. Express every result as NO₃ before comparing. Does the second method also read nitrate at or below detection? (Note: Do not average disagreeing methods and do not act on the lower number to be safe: both paths treat noise as signal.)
YES → block 7 · NO → block 6

Block 6 — Your methods disagree: resolve the measurement before touching the tank. Retest carefully; if a hobby kit and an ICP result still disagree after a careful repeat, escalate with both results and the kit's brand, age, and reporting basis (NO₃ vs NO₃-N). Run this procedure again once your methods agree.
END — ESCALATE RETEST

Block 7 — Look at what is growing. Is the dominant nuisance growth a red, maroon, or dark slime mat (cyanobacteria) rather than hair or film algae?
YES → block 8 · NO → block 9

Block 8 — Nitrate is confirmed at or below detection while a cyanobacteria-type mat is spreading. Escalate to Decode with your full ICP result, your nitrate and phosphate test records, and photos of the growth. Do not dose nitrate based on this procedure. (Why this procedure stopped: Cyanobacteria can fix nitrogen and thrive where nitrate tests read zero, so a spreading mat is not evidence that nitrate is available to the rest of the tank; and raising nitrate to outcompete it is a guess this procedure cannot underwrite.)
END — ESCALATE DECODE

Block 9 — Are you running carbon dosing (vodka, vinegar, NOPOX, or similar)? Carbon dosing feeds bacteria that consume nitrate: it is the first suspect when nitrate bottoms out.
YES → block 10 · NO → block 13

Block 10 — Is the program fully documented: known product, concentration, current daily dose, tank volume, and a dated log of how the tank has responded?
YES → block 12 · NO → block 11

Block 11 — This procedure cannot safely advise you while an unmeasured carbon-dosing program is running. Document the program fully (product, dose, volume, dated test results), then run this procedure again. (Why this procedure stopped: Advising a dose reduction on top of an unquantified carbon-dosing program is unsafe without knowing the product, its concentration, the current daily dose, tank volume, and how the tank has responded so far. This is a coverage gap, not a recommendation to start or stop carbon dosing.)
END — UNSUPPORTED METHOD

Block 12 — Reduce the documented daily carbon dose by one measured step and hold everything else constant. Do not stop the program outright: an abrupt stop swings nutrients in both directions and makes the result unreadable. Write down the old dose, the new dose, and the date. (Note: This check window is BioForge procedure policy, not a biological constant.) (Verify — 7 days, NITRATE: The reduced dose was held unchanged for the full window AND a comparable nitrate test reads detectable without exceeding the applicable upper boundary for your tank type.)
verified resolved → done · problem continues → block 1

Block 13 — Have you added or intensified nutrient export recently: a larger or re-tuned skimmer, a new refugium or algae reactor, additional filter media, or a more aggressive water-change schedule?
YES → block 14 · NO → block 15

Block 14 — Dial back the most recent export change by one measured step: shorten the refugium photoperiod, run the skimmer drier, or reduce media contact per the manufacturer's instructions. Change one thing, write down what and when, and keep it changed: nitrate responds slowly, and reverting halfway makes the result unreadable. (Note: This check window is BioForge procedure policy, not a biological constant.) (Verify — 7 days, NITRATE: The documented change was maintained for the full window AND a comparable nitrate test reads detectable without exceeding the applicable upper boundary for your tank type.)
verified resolved → done · problem continues → block 1

Block 15 — Has nitrogen input fallen: feeding reduced in amount or frequency, livestock removed or lost, or the tank lightly stocked relative to its size and coral load?
YES → block 16 · NO → block 17

Block 16 — Restore nitrogen input through feeding, not through a bottle. Increase feeding gradually (one small, logged step at a time) and let the tank's own biology convert it. Do not dose nitrate salts based on this procedure. (Note: This check window is BioForge procedure policy, not a biological constant.) (Verify — 14 days, NITRATE: The increased feeding was maintained for the full 14 days AND two comparable nitrate tests across that window read detectable without exceeding the applicable upper boundary for your tank type.)
verified resolved → done · problem continues → block 1

Block 17 — Check the other nutrient. Is phosphate also at zero or below detection: measured with an appropriate low-range method or your ICP result?
YES → block 18 · NO → block 19

Block 18 — Nitrate and phosphate are both confirmed at or below detection. Escalate to Decode with your full ICP result and both test records. Do not dose nitrate or phosphate based on this procedure, and do not intensify nutrient export. (Why this procedure stopped: This procedure cannot safely tell whether the tank is genuinely starved of both nutrients or whether the measurements are at their limits; and research on reef corals shows nutrient starvation and skewed nutrient availability can worsen coral condition and bleaching susceptibility.)
END — ESCALATE DECODE

Block 19 — Nitrate remains confirmed at or below detection, but this procedure did not isolate the cause. Escalate with the complete test history, tank profile, equipment list, feeding record, and the elimination trail from this procedure. (Why this procedure stopped: This procedure checked measurement, cyanobacteria attribution, carbon dosing, export intensity, and nitrogen input, and none of them explained the confirmed zero: the remaining causes need multi-parameter analysis, not another guess.)
END — ESCALATE DECODE