Setup path, stage 2

Reef tank equipment list by tank size

What you need on day one, what can wait until the first corals, and the safety kit people skip and then regret. Sized for a nano, a mid-sized tank and a large tank with a sump.

Last checked 21 October 2026. How we check

What equipment do I need for my tank size?

Which kit stops a tank crashing?

The failures that end tanks are mechanical: a heater stuck on, a top-off pump that runs dry or never stops, a power cut. Three cheap items cover most of it.

• An auto top-off (ATO) with a second, independent sensor. Evaporation leaves the salt behind, so without top-off salinity climbs, fastest in small tanks. BRS says top-off water must be 0 TDS RO/DI and suggests keeping most reservoirs at or under about 10 US gallons (38 litres) so a stuck pump cannot dump too much fresh water.
• Heaters on a controller. Split the wattage across two heaters and size the biggest so that, stuck on, it cannot push the tank more than 2 to 3 C over your set point (our rule; no source models this).
• A battery air pump or a battery-powered wavemaker. BRS says a tank with water movement can last two to three days without heat, filtration or light.

What size heater does a UK reef tank need?

US guides say 3 to 5 watts per US gallon, which is about 0.8 to 1.3 watts per litre. UK and European retailers size by room temperature instead: about 1 watt per litre in a heated room near 19 C, 1.5 watts per litre at 15 to 18 C, and up to 2.5 watts per litre in a room that drops to 13 or 14 C (typical, check). A lid makes a large difference. In a UK winter with the heating off at night, size for the cold room, not the warm one. The heater size calculator does the sums for your room.

How much light and flow does a reef need?

Light is measured as PAR at the coral. BRS (2025) suggests about 75 to 150 for soft corals and LPS and 200 to 350 for SPS. Practical Fishkeeping says most corals do well at 100 to 300 and that many keepers run lights at about 75%. BRS suggests about 10 hours a day: an hour of ramp up, eight at peak and an hour down.

Flow is usually quoted as turnover, the tank volume moved per hour. Forum consensus is about 10 to 30 times for soft corals and LPS and 40 times or more for SPS (typical, check). Pump ratings are at zero height, so real flow is lower. Dead spots matter more than the number: detritus settling or red slime in one corner tells you flow is not reaching it.

What can wait until later?

• Calcium and magnesium test kits, until you add stony corals.
• A dosing pump, until water changes no longer hold alkalinity (see the methods compared).
• A PAR meter (many shops and clubs lend them).
• Reactors for carbon or phosphate remover, until a test shows you need them.
• A chiller, unless the room regularly passes 28 C.

What are the steps, in order?

1. List the kit for your size band from the table.
2. Buy the safety items first: ATO with backup sensor, heater controller, battery air pump.
3. Buy test kits from a seller with a fast turnover so the reagents are fresh, and write the opening date on each box.
4. Check the light can be dimmed and scheduled.
5. Keep receipts and manuals together; note each heater and pump install date.

Your checklist

Tick items as you go. Ticks are saved in this browser only and fill the depth gauge.

What test must pass before moving on?

What are the common mistakes?

• Spending the budget on the light and skipping the ATO and heater controller.
• One large heater with its own dial as the only protection.
• An ATO reservoir much bigger than the tank can safely take in one go.
• Calibrating a refractometer with RO water instead of 35 ppt fluid.
• Buying a dosing pump on day one.

Where do sources disagree?

Figures from sources read as a search summary only are shown as typical figures: check them before you rely on them. Found a mistake? Tell us how to fix it.