How to set up a reef tank: the full timeline

A reef tank is not a fish tank you add salt to — it is a small, stable ocean you build in stages. Rushed tanks crash; patient ones thrive. The whole process from empty glass to first coral runs about six to eight weeks, most of it spent waiting for bacteria you can't see. Here is the order that works, with the numbers that matter at each step.

Phase 1 — Plan the build (week 0)

Before you buy anything, decide three things: display size, coral type, and budget. They lock each other together — SPS wants strong light and 40–60× flow, which pushes you toward a sump system, which raises the budget. A soft-coral nano can live happily in an all-in-one (AIO) tank for a fraction of the cost.

Start from the reef tank equipment list to see the nine core categories, then use the System Builder to turn your tank, coral type and budget into a specific parts list. Get your true system volume — display plus sump — from the volume calculator, because every other item is sized off it.

Phase 2 — Install tank and equipment (week 1)

Set the tank on a level, load-rated stand. Plumb the sump and return pump if you went that route, and mount but don't yet run the light and powerheads. Two rules save grief here:

• Heaters: install two, on a controller. Give the system 3–5 watts per gallon split across both elements. A single heater failing hot or cold is a preventable disaster — size the wattage here.
• Return pump: size for about 5× net turnover at your real head height, counting 1 ft of head per vertical foot plus elbows. Max GPH on the box is at zero head; you never get it.

If you bought an AIO, your filtration is already in the back chamber — skip the sump and return pump entirely.

Phase 3 — Make saltwater and add rock and sand (week 1–2)

Never mix salt with tap water. Run it through an RO/DI unit first — tap chlorine, nitrate and phosphate feed algae for months. Mix salt into RO/DI water to a specific gravity of 1.025 (about 35 ppt) at 78°F, using the salt mix calculator to get the ratio right, and confirm it with a refractometer via the salinity conversion tool.

Add live or dry rock — aim for a porous aquascape with open flow, not a solid wall — and a shallow sand bed or bare bottom. Then bring the system up to temperature (76–78°F) and turn on flow.

Phase 4 — Cycle the tank (week 2–6)

Cycling grows the bacteria that convert toxic fish waste (ammonia) to nitrite, then to far less toxic nitrate. Add an ammonia source — bottled ammonia or a piece of food — and test every few days with an API Saltwater Master Kit. The cycle is complete when ammonia and nitrite both read zero within 24 hours of dosing ammonia, and nitrate is present. That typically takes two to six weeks. Do not rush it; do not add fish to "help." A dark, low-flow, ugly-algae phase in the middle is normal.

Phase 5 — Stock in order (week 6 onward)

Add life slowly and in this sequence, testing as you go:

• Cleanup crew first. Snails and hermits graze the diatom film that blooms after cycling. Size the crew to your tank with the cleanup crew calculator.
• A hardy fish or two next. Add one or two at a time and watch your nitrate; a new tank's bacteria colony is still small.
• Beginner corals last, once the tank is stable. Wait until alkalinity, calcium and salinity hold steady week over week. Start with forgiving species and place them by their light and flow needs — see best beginner corals.

When do you add a skimmer or dosing?

• Protein skimmer: add it when you move past soft corals to LPS or SPS. Size it with the ReefRig Skimmer Method — 1.5–2× system volume × bioload, and check it fits your sump.
• Dosing: not yet. Water changes replace alkalinity, calcium and magnesium until your corals burn through more than 0.4–0.5 dKH of alkalinity per day. When a weekly change can't keep up, size doses with the dosing calculator.

A realistic budget

Costs scale with the tank you chose in Phase 1. Use the build cost calculator for your exact list, but as rough anchors: a nano AIO reef runs about $700–$1,200, a mid 90-gallon mixed sump build lands near $5,000–$7,000 with livestock, and a 120-gallon-plus SPS system with backup power clears $12,000. The tank sets the number, so size it to the budget honestly at the start.

Turn your plan into a specific, sized parts list in the System Builder — it maps every phase above to real 2026 products at your budget.

Water-chemistry targets and cycle guidance reflect long-standing reef community consensus (BRS, Reef2Reef). Prices verified July 2026; re-check before purchase. This guide covers equipment and process only and makes no livestock health or survival claims.