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.
Read guide →Nitrogen cycle & cycling
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.
Read guide →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.
Read guide →Salinity & RO/DI
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.
Read guide →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.
Read guide →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.
Read guide →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.
Read guide →Reef conservation & science
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.
Read guide →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.
Read guide →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.
Read guide →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.
Read guide →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.
Read guide →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.
Read guide →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.
Read guide →Start here
New to reefing? Read the nitrogen cycle and salinity & RO/DI guides first, then the Big 3. Look up any abbreviation in the reef glossary, and turn test results into doses with the free calculator.
From the blog
- Best Reef Tank Test Kits (2026): Salifert vs Red Sea vs Hanna
- How to Raise Alkalinity in a Reef Tank Safely (dKH Guide)
All guides last reviewed 2026-10-15.