FAULT ISOLATION MANUAL · NUTRIENTS — NITRATE

NO3-001 · Nitrate highv1.2.1

Nitrate reads above the applicable upper boundary for your tank type. This sheet isolates why, the way an aircraft maintenance manual would: confirm the reading, cross the safety gates, classify urgency for your tank, then act. Answer each numbered block and the sheet lights the path.

WHAT YOU'LL NEED

Your nitrate test kit (plus your ICP result or a second method)
A phosphate test or low-range checker
TDS readings from your RODI unit, if you run one
Salt mix, mixing container, and the water-change calculator
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 — Is your nitrate reading above the applicable upper boundary for your tank type, above 15 ppm (mixed reef) or above 8 ppm (SPS-dominant)? (Note: Some methods report nitrate as nitrogen (NO₃-N), while this Manual uses nitrate as NO₃. Confirm the reporting basis before entering a value. NO₃ is approximately 4.43 times NO₃-N.)
YES → block 3 · NO → block 2

Block 2 — NO3-001 NOT ACTIVE (Why this procedure stopped: Your confirmed nitrate does not meet this procedure's high-nitrate entry condition. NO3-001 makes no determination about whether lower nitrate is appropriate for your aquarium. If nitrate is undetectable or repeatedly bottoming out, return to the Manual index and use NO3-002 when available.)
END — NO FAULT

Block 3 — Confirm the reading before acting on it. First, repeat the same test you already used (same kit, fresh sample, careful technique) to rule out a handling error. If you can, corroborate with your ICP result or another appropriate method. Express every result as NO₃ before comparing. Do all confirmed results agree that nitrate is above the applicable upper boundary for your tank type?
YES → block 5 · NO → block 4

Block 4 — Your results do not agree, or the repeat did not confirm the high reading. Do not average disagreeing methods and do not act on the higher number to be safe: both paths treat noise as signal. Retest carefully; if an ICP result and a hobby kit 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 5 — Are you running carbon dosing (vodka, vinegar, NOPOX, or similar) without a fully documented program: known product, concentration, current daily dose, tank volume, and a log of how the tank has responded?
YES → block 6 · NO → block 7

Block 6 — 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: Adjusting or adding nitrate treatment on top of unquantified carbon dosing is unsafe without knowing the product, its concentration, the current daily dose, tank volume, your export equipment, oxygenation, and how the tank has responded so far. This is not a recommendation to start or stop carbon dosing.)
END — UNSUPPORTED METHOD

Block 7 — Does your most recent ICP result or phosphate test show phosphate at zero, or below the reporting limit?
YES → block 8 · NO → block 10

Block 8 — Confirm with a second, appropriate phosphate measurement: a low-range phosphate checker, or your ICP result if a hobby kit read zero. Does phosphate remain undetectable?
YES → block 9 · NO → block 10

Block 9 — Nitrate is confirmed high while phosphate is confirmed undetectable. Escalate to Decode with your full ICP result and both nitrate and phosphate test records. Do not intensify nutrient export, and do not dose phosphate based on this procedure. (Why this procedure stopped: This procedure cannot safely tell whether your tank is genuinely starved of phosphorus or whether the measurement is at its limit; and pushing nutrient export harder in either case can harm corals: research on reef corals shows phosphorus starvation and skewed nutrient availability can worsen coral condition and bleaching susceptibility.)
END — ESCALATE DECODE

Block 10 — Is your tank SPS-dominant, mostly small-polyp stony corals, run lean?
YES → block 12 · NO → block 11

Block 11 — Is your confirmed nitrate 40 ppm or higher?
YES → block 13 · NO → block 19

Block 12 — Is your confirmed nitrate 30 ppm or higher?
YES → block 13 · NO → block 19

Block 13 — Plan the exchange before touching water. Open the water-change calculator, enter your current nitrate, your interim target, and your system volume, and record the proposed exchange size, including whether it is one change or a series. The safety checks that follow depend on knowing this size.
then → block 14

Block 14 — Check the replacement batch against the planned exchange: (1) test the batch for nitrate with a salt-water-appropriate method you have validated: no detectable nitrate; (2) match salinity and temperature to the tank; (3) record the tank's alkalinity and the batch's alkalinity, and work out where the planned exchange size would put the tank's alkalinity; (4) confirm the salt is fully dissolved and the batch fully mixed. Record all results.
then → block 15

Block 15 — Did the batch and plan pass every check: no detectable nitrate, salinity and temperature matched, salt fully dissolved and mixed, and the planned exchange keeps tank alkalinity inside the acceptable range for your tank type: 8–10 dKH (mixed reef) or 7–9 dKH (SPS-dominant)?
YES → block 18 · NO → block 16

Block 16 — Which check failed: did the replacement water itself show detectable nitrate?
YES → block 21 · NO → block 17

Block 17 — Fix the plan or the batch, not the tank. If the alkalinity projection failed, reduce or stage the exchange in the calculator and re-run the numbers, correct the batch, or choose a salt mix closer to your tank's parameters. If salinity, temperature, or mixing failed, re-match and let the batch dissolve and mix completely. Do not perform the exchange with a plan and batch that failed preflight: at critical nitrate the exchange is large, and a mismatched batch trades one emergency for another. If repeated attempts cannot produce a passing plan and batch, escalate to Decode with your recorded readings instead of performing an unsafe exchange. (Note: This check window is BioForge procedure policy, not a biological constant.) (Verify — 1 day, REPLACEMENT WATER: A freshly planned exchange and prepared batch pass all preflight checks: no detectable nitrate by a salt-water-appropriate validated method, salinity and temperature matched, the planned exchange keeps tank alkalinity inside the applicable range, salt fully dissolved and fully mixed.)
verified resolved → done · problem continues → block 1

Block 18 — Bring nitrate out of the critical zone by executing the calculated plan with the batch that passed preflight. Follow the exchange size and count from the water-change calculator: if you re-plan between changes, re-run the calculator rather than guessing. Use a series of smaller calculated changes rather than one very large exchange when a large one would swing temperature, salinity, or alkalinity. Let each change mix completely, retest, and repeat until you are below the critical value for your tank type. Water changes remove nitrate that has already accumulated; they do not fix whatever is producing it. Once you are out of the critical zone, run this procedure again from the start to isolate the source. (Note: This check window is BioForge procedure policy for confirming the exchange worked, not a biological constant.) (Verify — 1 day, NITRATE: After the changed water has fully mixed, a comparable nitrate test reads below the critical value for your tank type.)
verified resolved → done · problem continues → block 1

Block 19 — Test your replacement water, matching the method to the water: (1) RODI or top-off water, use a nitrate method appropriate for fresh water, and check your TDS readings; rising TDS after the DI stage is evidence the resin is exhausting. Do not apply a marine nitrate kit to pure RODI unless it is validated for fresh water. (2) Newly mixed salt water, fully dissolved, use the marine nitrate method you validated in the confirmation step. Record both readings and your TDS numbers.
then → block 20

Block 20 — Did either sample show detectable nitrate, or did TDS behavior show the RODI unit passing contaminants?
YES → block 21 · NO → block 22

Block 21 — Your replacement water is bringing nitrate in with it. Correct the component the evidence points to: if TDS rises after the DI stage, the resin is exhausting; if TDS rises before it, look at the membrane or prefilters; if RODI tests clean but the mixed salt water does not, the salt mix or mixing container is the entry point. Service or replace only what the readings and the manufacturer's guidance implicate: replacing everything at once hides which component failed. Do not add the contaminated water to the tank in the meantime. More than one contributor can exist: if tank nitrate does not begin to fall over your next comparable tests after the fix, run this procedure again. (Note: This check window is BioForge procedure policy, not a biological constant.) (Verify — 1 day, NITRATE: Replacement and source water show no detectable nitrate, each tested with a method appropriate to its matrix, before being added to the aquarium.)
verified resolved → done · problem continues → block 1

Block 22 — Is your nutrient export actually working? Check each one you run: skimmer producing normal skimmate volume and color; refugium macroalgae visibly growing, light on schedule; reactors or filter media within their service life; filter socks or floss changed on schedule.
YES → block 24 · NO → block 23

Block 23 — Restore the export path you found down: clean and re-tune the skimmer, restore refugium lighting and harvest overgrown macroalgae, replace exhausted media per the manufacturer's instructions, resume the sock or floss schedule. Fix what is broken before adding anything new. (Note: This check window is BioForge procedure policy, not a biological constant.) (Verify — 7 days, NITRATE: The equipment's function is directly confirmed (skimmate production, new macroalgae growth, or media within service life) AND a comparable nitrate test at day 7 is not higher than the test taken just after the repair.)
verified resolved → done · problem continues → block 1

Block 24 — Has nitrogen input risen, or is waste accumulating? Consider: feeding increased in amount or frequency; new or larger fish added; detritus built up in the sump, filter socks, or low-flow dead spots; an unnoticed loss decomposing somewhere.
YES → block 25 · NO → block 26

Block 25 — Reduce the excess you identified: return feeding to the earlier amount, siphon out the trapped detritus, remove the loss, or rehome livestock if stocking outran the system. 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 — 14 days, NITRATE: The documented change was maintained for the full 14 days AND two comparable nitrate tests across that window show nitrate is no longer increasing.)
verified resolved → done · problem continues → block 1

Block 26 — Nitrate remains confirmed above the applicable upper boundary, but this procedure did not isolate the source. 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 replacement-water contamination, export function, and nitrogen input, and none of them explained the confirmed elevation: the remaining causes need multi-parameter analysis, not another guess. Do not add another nitrate-control method based on this result alone.)
END — ESCALATE DECODE