A reef tank can look simple from the outside. The equipment behind it does the real work. This guide breaks down what you need and how to choose it.
Core life support: tank, filtration, and flow
Start with a stable tank and stand. For most beginners, 40 to 75 gallons is ideal. Larger water volume buffers mistakes. Aim for a sump if space allows. It hides gear and adds water volume.
Use a quality protein skimmer for most mixed reefs. Size it for 1.5 to 2 times your total volume. A 75-gallon display with a 20-gallon sump needs a skimmer rated near 150 to 200 gallons. Set the skimmer to pull dark tea skimmate. Adjust the water level slowly.
Plan strong, random flow for coral health. Target 20 to 40 times tank volume per hour. A 50-gallon tank often needs 1,000 to 2,000 GPH of total circulation. Use two wavemakers for crossflow. Avoid blasting sand or coral tissue.
- Place powerheads 4 to 8 inches below the surface.
- Clean pump wet sides every 4 to 6 weeks.
- Use a filter sock or roller to trap detritus early.
Common mistake: chasing “crystal water” with too much mechanical filtration. Dirty socks spike nitrate if ignored. Change socks every 2 to 3 days. If that is hard, consider a roller mat. Learn more in our reef tank maintenance schedule.
Lighting, heating, and automation for stability
Choose lighting based on coral goals. Soft corals need less intensity than SPS. A practical target is 75 to 150 PAR for softies. Aim for 150 to 250 PAR for LPS. Many SPS thrive at 250 to 350 PAR. Use a 9 to 10 hour peak photoperiod. Add 1 hour ramps if your light supports it.
Temperature stability matters more than the exact number. Keep 77 to 79°F with swings under 1°F daily. Use two heaters instead of one. Each heater should cover about 50% of the load. For a 75-gallon system, use two 150W heaters. Add an external controller for safety.
Top-off and monitoring reduce daily stress. An ATO keeps salinity stable. Keep salinity at 1.025 to 1.026 specific gravity. Use a refractometer and calibrate with 35 ppt fluid. Place the ATO sensor in a calm sump chamber. Keep the reservoir covered to reduce dust.
- Use drip loops on every power cord.
- Label plugs for pumps, heater, and lights.
- Test temperature alarms monthly.
Troubleshooting tip: if pH runs low, check room CO2 first. Improve surface agitation and skimmer air intake. Open a nearby window during peak hours. You can also run a refugium on a reverse light cycle. For more setup help, see our reef tank sump setup guide.
Water quality tools: RO/DI, testing, and dosing
Use RO/DI water for mixing salt and topping off. Aim for 0 TDS output. Replace DI resin when it rises above 1 to 2 TDS. Flush the membrane after long downtimes. Store mixed saltwater with a heater and pump. Mix for 12 to 24 hours before use.
Test the parameters that drive coral growth. Keep alkalinity at 7.5 to 9.0 dKH for mixed reefs. Keep calcium at 400 to 450 ppm. Keep magnesium at 1,250 to 1,400 ppm. Maintain nitrate at 2 to 15 ppm and phosphate at 0.03 to 0.10 ppm. Stability beats perfection.
Start dosing only when demand appears. Many tanks need it after 2 to 4 months. Track alkalinity daily for one week. If it drops more than 0.3 dKH per day, plan dosing. Use a two-part system or kalkwasser. Add dosing pumps for consistency.
- Never raise alkalinity more than 1.0 dKH per day.
- Calibrate dosing pumps every 3 months.
- Log tests in a notebook or app.
Real-world scenario: your LPS looks deflated and tips are pale. Test alkalinity first. A swing from 8.5 to 7.2 dKH can cause this. Correct slowly and check magnesium. Also inspect for clogged return pumps. More gear choices are covered in our reef tank equipment checklist.
Sources: Bulk Reef Supply Investigates (BRS), Reef2Reef community guides, Randy Holmes-Farley reef chemistry articles, manufacturer manuals for heaters, pumps, and RO/DI units.
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