Choosing fish for a mixed reef tank: how to select reef-safe species that won't harm corals, territory management, and recommended stocking combinations.
Key Takeaways
Choosing fish for a mixed reef tank: how to select reef-safe species that won't harm corals, territory management, and recommended stocking combinations.
"Mixed Reef" refers to a tank setup where corals and saltwater fish are kept together. While you can enjoy the beauty of corals alongside the movement of fish, selecting the wrong fish species risks coral predation.
To successfully maintain corals and fish together, the golden rule is to choose "Reef Safe" fish.
Reef Safe fish are those that don't eat, peck at, or cause undue stress to corals. However, individual variation exists, so "Reef Safe" is ultimately just a guideline.
Clownfish (Nemo Family) Ocellaris clownfish and Percula clownfish are prime examples of the most reef-safe fish. They're famous for their symbiotic relationship with host anemones, but can be kept without them. While territorial, they cause virtually no harm to corals.
Blue Damselfish A small schooling species with vibrant blue coloring. Peaceful with low aggression, they rarely peck at corals. However, they may quarrel over territory with their own species.
Gobies (Prawn Gobies, Watchman Gobies, etc.) Bottom-dwelling gobies benefit the tank by sifting through the substrate to prevent detritus buildup. They don't eat corals and often pair with pistol shrimp, creating an entertaining symbiotic partnership.
Dwarf Angelfish (Pygmy Angels) Small pomacanthid angelfishes are generally reef safe. However, large angelfish species (Flame angelfish, certain Centropyge species) may peck at corals, requiring caution.
Seahorses They don't eat corals at all, but suffer if water flow is too strong. They pair well with corals, though you'll need to install artificial gorgonia or similar structures for them to hold onto.
Butterflyfish Many species feed on coral polyps and are generally unsuitable for reef tanks. However, exceptions like the Scrawled Butterflyfish are reef safe.
Large Angelfish (Flame Angelfish, etc.) Beautiful but problematic—species like the Flame Angelfish may peck at soft corals. Individual variation is significant, so attempting this requires understanding the risks.
Triggerfishes They eat corals and crustaceans, making them unsuitable for mixed reefs.
In a mixed reef, keeping fish numbers low is essential for maintaining water quality. A general rule: For a 60cm tank (approximately 80 liters), the maximum is 3–5 small fish under 7cm in length.
Too many fish cause: - Increased nitrate and phosphate levels, impacting corals - Indirect coral damage from territorial disputes - Increased strain on protein skimmers
Natural Reef Style (60cm Tank) - Ocellaris clownfish × 2 - Dottyback or Flameback Angelfish × 1 - Goby × 1 (Watchman Goby, etc.)
Colorful Community Setup (90cm Tank) - Ocellaris clownfish × 2 - Blue damselfish × 3–5 (schooling) - Fairy Wrasse (male/female pair) × 3 - Goby + Pistol Shrimp pair × 1
The key to mixed reef success is: "Choose reef-safe fish and stock lightly." Before setting up, thoroughly research fish behavior and ensure you can quickly isolate problem fish if needed. Build your beautifully balanced coral and fish tank thoughtfully and with patience.
Find Coral listings related to this article on BreederDirect. Buy directly from verified breeders.
Aquarium Volume Calculator
Calculate water volume, weight, and heater wattage from tank dimensions
Water Quality Checker
Find compatible fish, shrimp, plants & corals based on pH, temperature & hardness
Lighting Calculator
Calculate optimal LED lighting based on tank size and plants/corals
Nitrogen Cycle Guide
Auto-calculate bacteria colonization timeline for new tank cycling