What to buy, how to set up, and what to stock in saltwater aquariums. Equipment lists, sizing rules, stocking ideas, and the most common mistakes.
Saltwater aquariums cover everything from FOWLR (fish-only with live rock) to mixed reefs to species-specific predator tanks. The hobbyist who succeeds at saltwater is willing to learn water chemistry beyond pH and ammonia - alkalinity, calcium, magnesium, phosphate, nitrate are all parameters you actively manage, not passive readouts. Salt-mix selection, RO/DI water, and protein skimming are non-optional.
Core stack: tank (reef-ready if 75+); sump; protein skimmer sized for your bioload; return pump; circulation pumps (gyre or vortech-style); LED reef lighting; ATO with reservoir; RO/DI water system; salt mix; refractometer; full reef-test kit (alk/Ca/Mg/PO4/NO3); heater with redundancy; controller (Apex, GHL, Hydros) once you exceed 60-90 gallons.
Light: depends on coral mix. SPS-dominant: 350+ PAR at frag rack, blue-shifted spectrum. Mixed reef: 200-350 PAR. Fish-only: any reasonable LED at moderate PAR. Filter: protein skimmer rated for 1.5x display volume + filter sock or roller filter; refugium for nitrate + phosphate export.
Stocking depends on tank size and goals. FOWLR can run aggressive predators; mixed reef wants peaceful species (clownfish, gobies, anthias, peaceful tangs at appropriate sizes); SPS-dominant reefs minimize fish bioload to keep nutrients low. Always research adult size + temperament BEFORE buying.
Most-common mistake: skimping on the protein skimmer. A skimmer rated for "your tank size" is too small once you fully stock; skimmers should be rated 1.5-2x your display volume.
A 75-gallon saltwater system runs $1,500-4,000 in equipment + $500-3,000 in initial livestock + $300-800/year in salt + supplements + replacement gear. Reef-tank costs scale roughly linearly with display volume.
Saltwater is harder than freshwater but not unreasonable for a careful beginner. Start with a 30-40 gallon FOWLR or simple mixed reef.
A backup heater. Single-point-of-failure on heaters is the #1 cause of reef-tank disasters. Run two undersized heaters with a controller instead of one full-sized.
4-8 weeks. Test ammonia + nitrite daily; both must read 0 within 24 hours of dosing 2 ppm ammonia before adding fish.
Saltwater to freshwater is straightforward (drain, scrub, refill). Freshwater to saltwater means stripping all hardscape and replacing rock + sand with marine equivalents.