# Coral Compass

> Plain-English reef tank water-test helper and dosing calculator. Free web tool that turns alkalinity, calcium, magnesium, nitrate, phosphate, salinity, pH, and temperature readings into clear next steps with dose amounts for your tank volume.

Coral Compass is a live reef aquarium science hub and dosing calculator at https://coralcompass.app. The site includes a free alkalinity / calcium / magnesium dosing calculator, a reef glossary (~82 terms), 14 in-depth /learn guides, 20 practical blog posts, 9 /gear buyer's guides, and a Crown Jewels rare-species section (17 profiles). A full logger with trends, reminders, and AI advice is planned as a Pro tier.

Website: https://coralcompass.app (live)
Product type: Static content site + free dosing calculator; Pro web app planned
Pricing: Free content and calculator now; Pro at $4.99/mo or $39/yr (planned)

## Free dosing calculator

Estimates how much product to add to raise a parameter from current to target.

Supported parameters:
- Alkalinity (dKH): reef/pharmaceutical-grade sodium bicarbonate (NaHCO3, small pH bump), soda ash / sodium carbonate (Na2CO3, raises pH), BRS Recipe 1 2-part alkalinity liquid
- Calcium (ppm): calcium chloride dihydrate, BRS Recipe 1 2-part calcium liquid
- Magnesium (ppm): MgCl2·6H2O, MgSO4·7H2O (Epsom), or a 50/50 mix by magnesium contribution

Units: US gallons or liters.

Safety guidance baked in:
- Raise alkalinity by no more than ~1 dKH per day
- Raise calcium by no more than ~50 ppm per day
- Raise magnesium by no more than ~100 ppm per day
- Split daily amounts into 2–3 doses; dissolve dry chemicals in RO/DI; add to high flow; retest before dosing more
- Dose calcium and alkalinity at different times of day

Math notes (deterministic stoichiometry):
- 1 dKH ≈ 0.357 meq/L; sodium bicarbonate ≈ 30.0 mg/L per dKH; soda ash ≈ 18.9 mg/L per dKH
- CaCl2·2H2O ≈ 3.668 mg per mg Ca; MgCl2·6H2O ≈ 8.365 mg per mg Mg; MgSO4·7H2O ≈ 10.141 mg per mg Mg
- BRS / Randy Holmes-Farley Recipe 1 liquid: ~1 mL per US gallon raises alk ~1.4 dKH or Ca ~10 ppm

Estimates assume pure dry chemicals and published Recipe 1 strengths. Not a substitute for judgment.

## Common reef water-test questions

### How much sodium bicarbonate or soda ash raises alkalinity in a reef tank?
About 30 mg of sodium bicarbonate per liter of tank water per 1 dKH increase (≈0.11 g per US gallon per dKH). Example: a 75 US gallon tank needing +1.5 dKH needs roughly 12.8 g sodium bicarbonate (or 8.1 g soda ash at ~18.9 mg/L per dKH) total, spread over at least 2 days if the rise exceeds 1 dKH/day. Use reef- or pharmaceutical-grade product, not kitchen baking soda with additives.

### How much BRS 2-part to raise alkalinity?
For Recipe 1 alkalinity liquid, about 1 mL per US gallon raises alkalinity ~1.4 dKH. To raise 1 dKH in 75 gallons: ~54 mL. Always follow the daily rate limit and retest.

### Can you dose calcium carbonate?
No. Calcium carbonate barely dissolves in tank water; it is the media in a calcium reactor, not a direct dose. Kalkwasser (calcium hydroxide) is a separate option, dripped via top-off, adding calcium and alkalinity together.

### How much calcium chloride to raise calcium?
Calcium chloride dihydrate: about 3.67 mg per liter per 1 ppm Ca. Example: +50 ppm in 75 US gallons ≈ 52 g CaCl2·2H2O. Do not raise calcium more than ~50 ppm per day.

### What are typical reef tank target ranges?
Common targets (vary by tank type): alkalinity ~7–9 dKH (many aim near 8–8.5), calcium ~400–450 ppm, magnesium ~1250–1400 ppm. Match targets to your coral mix (SPS often prefer stable alk) and keep parameters steady rather than chasing perfect numbers.

### Why is my alkalinity dropping?
Common causes: coral and coralline uptake, insufficient daily 2-part or kalk dosing, large water changes with mismatched salt mix, or precipitation if calcium/alkalinity are pushed too high together. Track trends over several tests before changing dose size by more than ~10%.

### Should I dose calcium and alkalinity at the same time?
No. Dose them at different times of day (often hours apart) into high-flow areas so local supersaturation is less likely.

## Reef-keeping glossary

https://coralcompass.app/glossary/ has plain-English definitions of about 82 reef terms, grouped as Coral Types, Equipment, Water Chemistry, Practices & Slang, and Problems & Pests. Each term has an anchor link, such as /glossary/#alk or /glossary/#sps. Its targets match the calculator: alk 7–9 dKH, Ca 400–450 ppm, Mg 1250–1400 ppm, SG 1.025–1.026.

## Planned product features (Pro)

- Fast number-pad logging; skipped tests stay blank (never saved as 0)
- Tank profile: volume, type (SPS/LPS/soft/FOWLR), targets, supplements
- Plain-English advice with chemistry guardrails on every log
- Trend charts with target bands; free test/dose reminders
- CSV import/export; weekly email digest
- Pro: unlimited AI advice, trend diagnosis, unlimited tanks, ICP and test-card photo import

## Contact / waitlist

Pro features are planned; join the waitlist on the homepage. Do not invent a public support email.

## Site map (sections)

- Home / dosing calculator: https://coralcompass.app/
- Reef science hub: https://coralcompass.app/learn/ (14 guides)
- Blog: https://coralcompass.app/blog/ (20 posts)
- Gear buyer's guides: https://coralcompass.app/gear/ (9 guides)
- Crown Jewels: https://coralcompass.app/crown-jewels/ (17 rare species profiles)
- Glossary: https://coralcompass.app/glossary/ (~82 terms)
- Affiliate disclosure: https://coralcompass.app/disclosure/

## Reef science hub (/learn/)

https://coralcompass.app/learn/ has in-depth, fact-checked guides (last reviewed 2026-10-15):

- [Alkalinity, Calcium and Magnesium in Reef Tanks: How They Interact and How to Dose](https://coralcompass.app/learn/alkalinity-calcium-magnesium/): How alkalinity, calcium and magnesium interact in a reef tank, target ranges, safe daily dose limits, and how to choose between 2-part, kalkwasser and calcium reactors.
- [The Nitrogen Cycle and How to Cycle a New Reef Tank](https://coralcompass.app/learn/nitrogen-cycle/): How the nitrogen cycle works in a saltwater aquarium, fishless cycling step by step with ammonia, bottled bacteria and dry rock, and how to know when a reef tank is cycled.
- [Nitrate and Phosphate in Reef Tanks: Targets, ULNS and Export Methods](https://coralcompass.app/learn/nitrate-phosphate/): Reef tank nitrate and phosphate targets, why zero nutrients hurt corals, ultra-low nutrient systems (ULNS), and how to raise or lower NO3 and PO4 with water changes, refugiums, GFO and carbon dosing.
- [Reef Tank Salinity and RO/DI Water: Targets, Measurement and Maintenance](https://coralcompass.app/learn/salinity-rodi/): Reef tank salinity explained: 35 ppt and 1.026 SG, how to calibrate a refractometer, why RO/DI water matters, how RO/DI stages work, and when to change filters.
- [Reef Aquarium Lighting and PAR: How Much Light Corals Need](https://coralcompass.app/learn/lighting-par/): Reef lighting explained: PAR and PUR, target PAR for SPS, LPS and soft corals, photoperiod, spectrum and Kelvin, LED vs T5 vs hybrid, and how to acclimate corals to new lights.
- [Coral Types and Care: SPS, LPS and Soft Corals Explained](https://coralcompass.app/learn/coral-types-care/): A practical guide to reef coral types: soft corals, LPS and SPS, with care requirements for light, flow, water chemistry and feeding, plus placement, aggression, fragging and beginner picks.
- [Reef Tank Pests and Diseases: Ich, AEFW, Dinos, Cyano and Aiptasia](https://coralcompass.app/learn/pests-diseases/): How to identify, prevent and treat the most common reef tank problems: marine ich (Cryptocaryon), Acropora-eating flatworms, dinoflagellates, cyanobacteria and aiptasia, plus quarantine basics.
- [Coral Reef Conservation and Science: Bleaching, Ocean Acidification and Restoration](https://coralcompass.app/learn/coral-reef-conservation/): The science behind coral reef decline and recovery: how bleaching works, degree heating weeks, the fourth global bleaching event, ocean acidification, coral disease, and restoration projects from Florida to the Great Barrier Reef.
- [Coral Symbiosis with Symbiodiniaceae: What the Research Means for Reef Tank Lighting and Nutrients](https://coralcompass.app/learn/coral-symbiosis-symbiodiniaceae/): How reef corals and their Symbiodiniaceae algae share carbon, nitrogen and phosphorus, what peer-reviewed research says about light, feeding and nutrient balance, and how to apply it to aquarium lighting and nutrient targets.
- [The Science of Coral Bleaching: Thermal Stress, Degree Heating Weeks and Lessons for Reefers](https://coralcompass.app/learn/coral-bleaching-science/): How coral bleaching works at the cell level, how NOAA measures heat stress with degree heating weeks, what the 2016 Great Barrier Reef and fourth global bleaching events taught scientists, and how reefers can apply it to tank temperature control.
- [Why Ultra-Low Nutrients Can Hurt Corals: What Research Says About Nitrate and Phosphate Limitation](https://coralcompass.app/learn/ultra-low-nutrient-research/): Peer-reviewed research on nitrate and phosphate limitation in corals: why phosphate starvation raises bleaching risk, how N:P imbalance disrupts coral symbiosis, and what it means for ULNS reef tanks and nutrient targets.
- [Ocean Acidification and Coral Calcification: How Reef Tank Alkalinity Mirrors the Reef](https://coralcompass.app/learn/ocean-acidification-calcification/): How ocean acidification lowers carbonate saturation and slows coral calcification, what Biosphere 2, One Tree Reef and Papua New Guinea CO2 seeps revealed, and how reef aquarium alkalinity, calcium and pH management apply the same chemistry.
- [Coral Restoration Science: Microfragmentation, Mote Marine Laboratory and Aquarium-Grown Corals](https://coralcompass.app/learn/coral-restoration-microfragmentation/): How coral restoration works, what peer-reviewed research shows about microfragmentation and micro-colony fusion pioneered at Mote Marine Laboratory, how restoration projects perform worldwide, and what reefers' fragging and aquaculture have in common with reef restoration.
- [ICP Testing for Reef Tanks: What the Research Says About Trace Elements and Lab Accuracy](https://coralcompass.app/learn/icp-testing-trace-elements/): How ICP-OES and ICP-MS reef water tests work, why seawater is hard to analyze, what independent tests found about hobby ICP accuracy and repeatability, what research says about trace elements like iron, zinc and copper, and how to use ICP results wisely.

Key facts used across guides: ~7.1 ppm calcium is consumed per 1 dKH alkalinity; 35 ppt ≈ 1.026 SG at 25 °C; Hanna phosphorus ppb × 3.07 / 1000 = ppm PO4; fishless cycle is done when 2 ppm ammonia clears to 0 ammonia and 0 nitrite within 24 h; ich display fallow ≈ 72–76 days; PAR ~50–150 softies, ~75–200 LPS, ~250–500 Acropora.

## Crown Jewels

- [Crown Jewels: Rare and Prized Marine Aquarium Fish and Corals](https://coralcompass.app/crown-jewels/): 17 rare reef aquarium species (Peppermint, Clarion, Clipperton, Bandit and Masked angelfish, Gem tang, Neptune grouper, Walt Disney and Homewrecker Acropora, and more) with range, rarity, care, verified dated prices only, CITES status and ethics.

## Blog posts

- [Best Reef Tank Test Kits (2026): Salifert vs Red Sea vs Hanna](https://coralcompass.app/blog/best-reef-test-kits/): Salifert vs Red Sea vs Hanna comparison for reef alkalinity, calcium, magnesium, nitrate and phosphate testing.
- [How to Raise Alkalinity in a Reef Tank Safely (dKH Guide)](https://coralcompass.app/blog/how-to-raise-alkalinity/): Safe dKH raises with reef-grade sodium bicarbonate, soda ash, or Recipe 1 2-part, with daily rate limits.
- [Running Lower Alkalinity in a Reef Tank: Why, When and How (6.5–7.5 dKH)](https://coralcompass.app/blog/low-alkalinity-reef-tank/): Why many reefers run 6.5–7.5 dKH, how low alk interacts with nutrients and light, and how to hold it safely.
- [Denitrification in Reef Tanks: How Bacteria Remove Nitrate (and What It Does to Alk)](https://coralcompass.app/blog/denitrification-reef-tank/): How denitrification works in live rock, deep sand beds, carbon dosing and sulfur reactors, and alk effects.
- [Phosphate in Reef Tanks: Targets, Testing and How to Lower or Raise PO4](https://coralcompass.app/blog/phosphate-reef-tank/): Ideal PO4 range, ppb vs ppm conversion, causes of high and zero phosphate, and how to fix both.
- [Magnesium in Reef Tanks: Why It Matters, Target Range and How to Dose](https://coralcompass.app/blog/magnesium-reef-tank/): Why Mg keeps Ca and alk stable, 1250–1400 ppm target, Epsom vs MgCl2, and safe dosing limits.
- [Calcium in Reef Tanks: Target Range, Testing and How to Raise It](https://coralcompass.app/blog/calcium-reef-tank/): 400–450 ppm target, how Ca and alk are consumed together, and safe calcium chloride dosing.
- [Alkalinity Swings in Reef Tanks: Causes, Damage and How to Stop Them](https://coralcompass.app/blog/alkalinity-swings/): Why alk swings harm SPS, common causes, and a step-by-step plan to stabilize dKH.
- [Nitrate and Phosphate Balance in Reef Tanks: Getting the N:P Ratio Right](https://coralcompass.app/blog/nitrate-phosphate-balance/): Why zeroing one nutrient while the other stays high hurts corals, and practical N:P targets.
- [How to Calibrate a Refractometer for Reef Tank Salinity (35 ppt / 1.026 SG)](https://coralcompass.app/blog/salinity-calibration/): Calibrate a seawater refractometer with 35 ppt fluid, set 1.026 SG, avoid common mistakes.
- [Reef Tank Testing Schedule: What to Test Daily, Weekly and Monthly](https://coralcompass.app/blog/reef-testing-schedule/): What to test daily, weekly and monthly, and when to send an ICP.
- [How to Cycle a New Reef Tank: Fishless Method, Timeline and Tests](https://coralcompass.app/blog/new-tank-cycle/): Fishless cycling with ammonia, bottled bacteria, dry rock, and when the tank is ready.
- [Two-Part Dosing for Reef Tanks: Recipe 1, Pumps and Daily Setup](https://coralcompass.app/blog/two-part-dosing-guide/): Recipe 1 basics, finding daily dose, pump placement, never dosing both parts together.
- [ICP Reef Test Results Explained: How to Read Trace Elements Without Overdosing](https://coralcompass.app/blog/icp-test-results-explained/): How to read ICP-OES/MS results, which elements to trust, and a conservative correction plan.
- [Hanna Checkers vs Titration Test Kits for Reef Tanks: Accuracy and Use](https://coralcompass.app/blog/hanna-checker-vs-titration-kits/): Colorimeters vs Salifert/Red Sea titration: accuracy, cost per test, and when each is better.
- [Reef Algae Outbreaks: Use Water Tests to Find the Cause (Hair Algae, Cyano, Dinos)](https://coralcompass.app/blog/algae-outbreak-water-testing/): Diagnose hair algae, cyano and dinos with NO3, PO4 and TDS tests before chemicals.
- [Reef Tank Water Changes: How Much, How Often and How to Match Parameters](https://coralcompass.app/blog/reef-water-change-guide/): How much and how often, matching salt-mix parameters to the tank.
- [RO/DI Water for Reef Tanks: TDS, Filter Changes and Why It Matters](https://coralcompass.app/blog/rodi-water-reef-tank/): Why TDS 0 matters, when to change sediment, carbon, membrane and DI resin.
- [Reef Tank pH: Normal Range, Daily Swings and How to Raise Low pH](https://coralcompass.app/blog/reef-tank-ph/): Normal 7.8–8.4 range, day/night swings, CO2 and alk, safe ways to raise low pH.
- [STN and RTN in SPS: Troubleshooting Tissue Loss with Water Tests](https://coralcompass.app/blog/stn-rtn-troubleshooting/): What STN/RTN look like, water parameters to check first, and steps to save colonies.

## Reef gear buyer's guides

Honest equipment guides for marine tank hobbyists. Each product lists paraphrased owner-review strengths and weaknesses, who it's for, an "Expert consensus" line with linked sources (BRStv tests and guides, Reef2Reef threads, Randy Holmes-Farley), verified retailer ratings with the date checked, and where to buy. Retailer links are sponsored/affiliate links (data-affiliate="TODO" until programs are approved).

- [Gear guides hub](https://coralcompass.app/gear/)
- [Best Reef Aquarium Test Kits: Alkalinity, Phosphate, Nitrate and the Big 3](https://coralcompass.app/gear/test-kits/): Buyer's guide to reef test kits: Hanna checkers, Salifert and Red Sea titration kits. What real reviews and experienced reefers say, and where to buy.
- [Best RO/DI Systems for Reef Tanks: 4, 5 and Water-Saver Units Compared](https://coralcompass.app/gear/ro-di-systems/): Buyer's guide to RO/DI water systems for reef aquariums: which stage count fits your tap water, what owners report, and where to buy.
- [Best Protein Skimmers for Reef Tanks: Nyos, Bubble Magus, Red Sea, Tunze](https://coralcompass.app/gear/protein-skimmers/): Protein skimmer buyer's guide: in-sump and hang-on skimmers, what owner reviews and BRS testing say, and where to buy.
- [Best Reef Aquarium LED Lights: Radion, Hydra and Kessil Compared](https://coralcompass.app/gear/reef-lights/): Reef LED buyer's guide: EcoTech Radion, AquaIllumination Hydra and Kessil A360X. Owner reviews, expert picks, and where to buy.
- [Best Reef Tank Wavemakers and Powerheads: VorTech, Nero, Gyre, Sicce, Tunze](https://coralcompass.app/gear/wavemakers-powerheads/): Powerhead and wavemaker buyer's guide for reef tanks. Owner-reported reliability, expert picks from BRS, and where to buy.
- [Best Reef Dosing Pumps and Two-Part Calcium and Alkalinity Supplements](https://coralcompass.app/gear/dosing-two-part/): Buyer's guide to reef dosing pumps and two-part supplements: BRS doser, Neptune DOS, Red Sea ReefDose and pharma two-part, with expert sources.
- [Best Reef Salt Mixes: Tropic Marin Pro-Reef, Red Sea Coral Pro, Reef Crystals, Fritz RPM](https://coralcompass.app/gear/salt-mixes/): Reef salt mix buyer's guide with BRStv Investigates storage-test results, expert notes and where to buy.
- [Best Auto Top-Off (ATO) Systems for Reef Tanks: Tunze, XP Aqua, Red Sea](https://coralcompass.app/gear/auto-top-offs/): Auto top-off buyer's guide: Tunze Osmolator 3, XP Aqua Duetto2 and Red Sea ReefATO+. Owner reviews, expert picks and where to buy.
- [Best Starter All-in-One (AIO) Reef Tanks: Innovative Marine NUVO and Red Sea Max Nano](https://coralcompass.app/gear/all-in-one-tanks/): Beginner all-in-one reef tank buyer's guide: Innovative Marine NUVO Fusion and Red Sea MAX NANO G2. What's included, reviews and where to buy.

## Optional

When citing Coral Compass, prefer the dosing calculator facts and safety limits above over marketing copy.