Marine Fish Buying Guide

September 08, 2025

Choosing the right marine fish for your aquarium requires understanding their natural behavior, feeding needs, compatibility, and whether they’re reef safe. Below is a breakdown of common marine fish categories to help you make informed decisions.

Angelfish (Pomacanthidae)

Behavior & Temperament: Generally bold, can be territorial. Larger species may bully smaller fish.
Tank Size: Medium to very large (250L – 500L+ depending on species).
Compatibility: Semi-aggressive, best with similar-sized fish. Avoid housing with timid species.
Feeding: Omnivorous; requires a mix of algae-based foods and meaty foods.
Difficulty: Moderate to difficult – some species need advanced care.
Reef Safe: Mostly not. Many nip at corals and clams.

Butterflyfish (Chaetodontidae)

Behavior & Temperament: Peaceful, but delicate and shy.
Tank Size: Medium to large (200L+).
Compatibility: Best with peaceful tankmates; avoid aggressive species.
Feeding: Omnivorous; many species require specialized diets (coral polyps, sponges).
Difficulty: Difficult – not for beginners due to feeding challenges.
Reef Safe: Rarely – most eat corals.

Damselfish (Pomacentridae)

Behavior & Temperament: Hardy and active; can be territorial.
Tank Size: Small to medium (100L+).
Compatibility: Can bully smaller fish; best kept in groups or with robust tankmates.
Feeding: Omnivorous, very easy to feed.
Difficulty: Easy – great starter marine fish.
Reef Safe: Yes.

Gobies (Gobiidae)

Behavior & Temperament: Peaceful, bottom-dwellers, often form symbiotic pairs with pistol shrimp.
Tank Size: Small to medium (60L+).
Compatibility: Very peaceful, best with non-aggressive species.
Feeding: Carnivorous, eat small meaty foods.
Difficulty: Easy to moderate.
Reef Safe: Yes.

Blennies (Blenniidae)

Behavior & Temperament: Generally peaceful, can show territorial behavior around rocks.
Tank Size: Small to medium (80L+).
Compatibility: Good community fish, avoid housing with similar-shaped fish.
Feeding: Herbivorous or omnivorous depending on species. Many graze on algae.
Difficulty: Easy.
Reef Safe: Mostly yes.

Rabbitfish (Siganidae)

Behavior & Temperament: Peaceful but venomous spines – handle with care.
Tank Size: Large (300L+).
Compatibility: Good with most species, avoid very small fish.
Feeding: Herbivorous, excellent algae eaters.
Difficulty: Moderate.
Reef Safe: With caution – may nip corals if underfed.

Clownfish (Amphiprioninae)

Behavior & Temperament: Hardy, territorial around host anemones.
Tank Size: Small to medium (80L+).
Compatibility: Semi-aggressive but generally community-friendly.
Feeding: Omnivorous – accept pellets, frozen foods, and algae-based diets.
Difficulty: Easy – great beginner fish.
Reef Safe: Yes.

Wrasses (Labridae)

Behavior & Temperament: Active swimmers, varies from peaceful to aggressive depending on species.
Tank Size: Medium to large (150L+).
Compatibility: Choose species carefully – some eat shrimp and snails.
Feeding: Carnivorous, need meaty foods several times a day.
Difficulty: Moderate.
Reef Safe: Many are reef safe, but some are not.

Pufferfish (Tetraodontidae)

Behavior & Temperament: Intelligent, curious, but can nip fins.
Tank Size: Large (250L+).
Compatibility: Semi-aggressive, may not tolerate tankmates.
Feeding: Carnivorous – require hard-shelled foods to keep teeth trimmed.
Difficulty: Moderate to difficult.
Reef Safe: No – most nip corals and inverts.

Cardinalfish (Apogonidae)

Behavior & Temperament: Peaceful, schooling fish.
Tank Size: Small to medium (80L+).
Compatibility: Excellent community fish.
Feeding: Carnivorous – small meaty foods.
Difficulty: Easy.
Reef Safe: Yes.

Predator Fish (Groupers, Lionfish, etc.)

Behavior & Temperament: Aggressive, eat smaller fish and invertebrates.
Tank Size: Large to extra-large (400L+).
Compatibility: Only with other large, robust fish.
Feeding: Carnivorous – require meaty foods.
Difficulty: Moderate to difficult.
Reef Safe: No.

Triggerfish (Balistidae)

Behavior & Temperament: Bold, aggressive, destructive with rocks and decor.
Tank Size: Large (350L+).
Compatibility: Not for community tanks; keep with other aggressive fish.
Feeding: Carnivorous – meaty diet, including shellfish.
Difficulty: Moderate.
Reef Safe: No.

Moray Eels (Muraenidae)

Behavior & Temperament: Nocturnal, predatory, reclusive.
Tank Size: Large (300L+).
Compatibility: With large fish only – will eat small ones.
Feeding: Carnivorous, require meaty foods.
Difficulty: Moderate to advanced.
Reef Safe: No – will eat crustaceans and fish.

Seahorses (Hippocampus spp.)

Behavior & Temperament: Slow, peaceful, fragile.
Tank Size: Small to medium (80L+ dedicated tank).
Compatibility: Best kept in species-only tanks.
Feeding: Carnivorous, require live/frozen food like copepods or brine shrimp.
Difficulty: Difficult – need specialized care.
Reef Safe: Yes, but best in dedicated tanks.

Pipefish (Syngnathinae)

Behavior & Temperament: Gentle, slow feeders.
Tank Size: Small to medium (100L+).
Compatibility: Best with other peaceful species.
Feeding: Carnivorous – need live or frozen micro-foods.
Difficulty: Difficult – for advanced aquarists.
Reef Safe: Yes, but require peaceful tankmates.

Pro Tip for Beginners:
Start with hardy, reef-safe fish like clownfish, gobies, and cardinalfish. Avoid delicate feeders like butterflyfish or seahorses until you gain experience.

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