The Complete Guide to Coral Reef Tanks

A reef tank is one of the most rewarding projects in the aquarium hobby, combining fish, invertebrates, and living coral in a single closed ecosystem. It’s also one of the more technical setups, so understanding the fundamentals up front saves a lot of frustration.

Choosing Your Coral Types

Soft corals, such as Xenia and mushroom corals, are generally the most forgiving for beginners. LPS (large polyp stony) corals like Euphyllia are a good next step, while SPS corals like Waving Hand – Blue Xenia and other corals demand very stable, high-quality water. See our species-specific Acropora care guide for SPS specifics.

Lighting

Coral relies on symbiotic algae (zooxanthellae) for much of its energy, so appropriate reef lighting is non-negotiable. LED reef fixtures with adjustable spectrum and intensity let you match light output to each coral’s needs as your tank matures.

Water Flow

Corals need moderate to strong, randomized water movement to keep detritus off their tissue and deliver food particles. Powerheads placed at varying angles typically work better than a single strong point source.

Water Chemistry: Calcium, Alkalinity, and Magnesium

Stony corals build their skeletons from calcium carbonate, so maintaining calcium (~380-450 ppm), alkalinity (~8-12 dKH), and magnesium (~1250-1350 ppm) in balance is critical. Test weekly and dose consistently rather than in large corrective swings.

Protein Skimming

A quality protein skimmer removes dissolved organics before they break down into nitrate and phosphate, both of which fuel algae growth that competes with coral for light and nutrients.

Stocking Order

Cycle your tank fully (see How to Cycle a New Aquarium), then add a clean-up crew, followed by hardy fish, and only add coral once parameters have been stable for several weeks.

For further reading on coral biology, see the Wikipedia entry on coral.