Less guessing. More math.
Most reef-tank failures come from two places: a build decision that didn't survive contact with reality, and a budget that didn't survive contact with shipping. The planner kills both. Here's exactly what the engine checks, in the order it checks it.
How the engine actually decides.
ReefCrafter is a deterministic checker, not a recommender. It reads the build you assembled, runs each rule against published specs and well-known reef-keeping benchmarks, and shows you what fired and why. Same input, same output — every time.
Read the build
The engine pulls real values from the gear you added: skimmer rated_max_gallons, total heater wattage, return-pump GPH, light count and footprint, plus tank gallons, reef goal, and bioload tier. No hidden inputs.
Run every applicable rule
Each rule has an applies_when filter and a condition (LHS op RHS). Heater rules don't fire unless tank gallons are set. Skimmer rules scale by bioload tier. Rules that don't apply are skipped, not silently downgraded.
Show what fired and why
Every finding links back to its rule key and the values it pulled from your build. Warnings can be overridden with a written reason that stays attached to the saved build. Hard-physics safety rules can't be silenced.
Three classes of finding.
Every rule fires at one of three severities. Errors block the build until you address them; warnings and advisories don't.
Errors · 2 live
Real risks — cooked livestock, flooded floors, broken gear. The build shouldn't ship until these are addressed.
Warnings · 13 live
The build will work but you're at the edge of recommended specs. Step up the gear if you can.
Advisories · 8 live
Community wisdom. AIO + SPS is harder. Single-light SPS is suboptimal. Worth knowing, not blocking.
What the engine actually checks.
Every rule is open source. Click into a build and the planner fires these against your spec live; the warning links to the exact rule and the values it pulled from your build.
Declarative, not magical.
Each rule is a JSON object with a key, a severity, and a condition. No ML, no "trust us." If a rule fires on your build you can read the condition and verify it matched.
Re-runs on every change.
Swap the tank, all downstream rules re-evaluate. Skimmer rating rechecked, flow turnover recomputed, heater band reassessed. No stale numbers.
Open-source.
The full ruleset is in rules.json. Spot a rule that's wrong, or one we're missing? Email rules@reefcrafter.com or open an issue. Suggestions are reviewed before they ship — community input shapes the backlog, it doesn't auto-publish.
Display volume, sump volume, stand load, and footprint. The tank is the constraint everything else has to live inside.
PAR coverage matched to your tank footprint. Corner shadowing flagged. Light count vs SPS-tier coverage required.
Real GPH after head-loss, not box rating. Quiet-mode throughput counted separately.
Rated capacity scaled by your bioload tier. A skimmer that "fits the gallons" isn't enough if the bioload is heavy.
Total turnover by reef type — 10× softie, 30× mixed, 40×+ SPS. Glass-mount vs gyre placement noted.
Watts per gallon held inside the safe band, with redundancy required on tanks 50g and up.
Reservoir capacity vs evap rate. Dosing-pump throughput vs daily demand for two-part / kalk regimes.
The honest limits of a pre-buy check.
ReefCrafter is a sanity check on the gear and goals you wired into the planner. It is not omniscient and it is not a replacement for the slow parts of reef-keeping.
It only sees what you entered.
The engine reads your tank gallons, gear, reef goal, and bioload tier. It can't see your room temperature, your water source, your maintenance habits, your acclimation routine, or your real-world flow patterns once rockwork is in.
The ruleset is hardware-first.
Most live rules cover gear sizing. Livestock-specific compatibility checks are in the planner and still expanding. A clean compatibility report is not a green light to add aggressive fish or sensitive corals on day one.
Manufacturer ratings are optimistic.
Skimmer 'rated for' values, light coverage claims, and pump GPH numbers are best-case figures. The engine deliberately scales them by bioload, head loss, and reef goal — but no rule replaces watching your actual tank.
It can’t cycle your tank for you.
Compatibility passing means the build is internally consistent. It does not mean the tank is ready for livestock. Cycling, parameter stability, and slow stocking still matter — and always will.
The ruleset is evolving.
ReefCrafter is in open beta. New rules ship as we hit edge cases the engine missed; existing rules get tightened when they fire too aggressively. Saved builds re-evaluate against the current ruleset, so today's pass can become tomorrow's warning.
It doesn’t pick a winner for you.
The engine flags risk; it doesn't rank brands or tell you the 'best' skimmer. Vendor links exist when ready, but the recommendation is whatever fits the build — not whatever pays the highest commission.
Push back on a rule. We’d rather hear it now.
Reef-keeping accumulates know-how that no spec sheet captures. If a rule fires on a build you know works, or stays quiet on a build you know doesn’t, tell us. Suggestions, edge cases, and long-tank experience all feed the backlog.
Important: ReefCrafter is not a crowdsourced engine. Every suggestion is reviewed against published specs, manufacturer data, and accepted reef-keeping practice before anything ships. Community input shapes the backlog — it does not auto-publish rules.
- The build: tank gallons, reef goal, the specific gear, and bioload tier.
- The finding: which rule fired (or didn’t) and what you expected instead.
- The math: the ratio, threshold, or spec reference behind your suggestion.
- The receipts: manufacturer link, long-running tank context, or a published reef-keeping source where possible.
Turn the rules into pre-buy checks.
If you are not ready to open the full planner yet, start with the expensive weak spots: skimmer capacity, flow, lighting, heaters, and the final cart review.
Open the planner. Break something.
Spec a 30 gallon and try to fit a 200W heater. Add a single skimmer rated for half your bioload. Watch the engine politely refuse.