Free tool
Saltwater fish compatibility checker
"Will these get along?" Tick the fish you're considering — we check every pair for the clashes that actually matter: two tangs, mixed clownfish, aggressor-vs-timid, and tank size — straight from our fact-checked care guides. Check before you buy, not after.
How this works
Every fish's temperament, minimum tank size and own-kind rule comes straight from its Coralkin care guide, so the checker can never contradict the full guide. It flags the big, well-established conflicts (one-tang-per-tank, don't-mix-clownfish, semi-aggressive fish harassing timid ones, and fish that need a bigger tank than you have) — it doesn't try to predict every individual personality. When in doubt, add the calmer fish first and the pushier fish last.
A free Coralkin tool — no sign-up, nothing saved. It reasons only over facts we've sourced and cited. We never guess a care number.
Fish compatibility & temperament at a glance
Every fish we cover, with its temperament, minimum tank and own-kind rule — from its fact-checked care guide. Use this to shortlist, then tick your picks above for the pairwise check on your list.
| Fish | Temperament | Min tank | Keep as | Reef-safe? |
|---|---|---|---|---|
| Banggai Cardinalfish | Peaceful, timid | 20 gal | One, or a bonded pair | Yes |
| Bicolor Blenny | Peaceful | 10 gal | One per tank | With caution |
| Blue Tang | Peaceful | 100 gal | One tang per tank | Yes |
| Coral Beauty Angelfish | Peaceful | 70 gal | One dwarf angel per tank | With caution |
| Firefish Goby | Peaceful, timid | 20 gal | One, or a bonded pair | Yes |
| Flame Angelfish | Peaceful | 70 gal | One dwarf angel per tank | With caution |
| Flame Hawkfish | Semi-aggressive | 30 gal | One per tank | With caution |
| Green Chromis | Peaceful | 30 gal | A group of 6+ | Yes |
| Green Clown Goby | Peaceful, timid | 10 gal | One, or a bonded pair | With caution |
| Kole Tang | Peaceful | 70 gal | One tang per tank | Yes |
| Lawnmower Blenny | Peaceful | 30 gal | One per tank | Yes |
| Lyretail Anthias | Peaceful | 70 gal | A group of 3+ | Yes |
| Mandarin Dragonet | Peaceful, timid | 30 gal | One per tank | Yes |
| Melanurus Wrasse | Peaceful | 55 gal | One per tank | With caution |
| Midas Blenny | Peaceful | 30 gal | One per tank | Yes |
| Neon Goby | Peaceful | 10 gal | One, or a bonded pair | Yes |
| Ocellaris Clownfish | Peaceful | 15 gal | One, or one bonded pair | Yes |
| Orchid Dottyback | Peaceful | 20 gal | One per tank | Yes |
| Pajama Cardinalfish | Peaceful, timid | 20 gal | A group of 5+ | Yes |
| Percula Clownfish | Peaceful | 15 gal | One, or one bonded pair | Yes |
| Powder Blue Tang | Semi-aggressive | 125 gal | One tang per tank | With caution |
| Royal Gramma | Peaceful | 20 gal | One per tank | Yes |
| Six Line Wrasse | Semi-aggressive | 30 gal | One per tank | With caution |
| Tailspot Blenny | Peaceful | 10 gal | One per tank | Yes |
| Yellow Tang | Peaceful | 90 gal | One tang per tank | Yes |
| Yellow Watchman Goby | Peaceful | 20 gal | One, or a bonded pair | Yes |
"With caution" = reef-safe with corals but with an invert or coral-nipping caveat — see the fish's guide for the specifics. Every figure traces to that fish's fact-checked care guide.
Common compatibility questions
Can two clownfish live together?
Only as a single bonded pair of the SAME species — keep one clownfish, or one pair. Two different clownfish species (or two unpaired adults) fight over territory, so don't mix clownfish. Clownfish are otherwise peaceful toward unrelated fish.
Can you keep two tangs in one tank?
As a rule, one tang per tank. Tangs are peaceful toward other fish but territorial toward other tangs and surgeonfish, so two usually fight — the exception is a very large tank (90–125 gal+) with both added together as juveniles. A yellow tang needs 90 gal, a blue tang 100 gal, a powder blue tang 125 gal.
Can clownfish live with tangs, gobies and wrasses?
Yes — clownfish are peaceful and get along with most non-clownfish, including tangs, gobies, blennies, cardinalfish and most wrasses, as long as the tank meets the largest fish's minimum size. The clashes to watch are same-group (two tangs, two dwarf angels, mixed clownfish) and semi-aggressive fish (six-line wrasse, flame hawkfish, powder blue tang) harassing timid tankmates. Use the checker above for your exact list.
What saltwater fish are reef-safe?
Most beginner-friendly marine fish are reef-safe with corals — clownfish, gobies, cardinalfish, chromis, tangs and blennies. But "reef-safe" isn't always "invert-safe": the six-line and melanurus wrasses pick at ornamental shrimp, pods and small snails; the flame hawkfish eats small shrimp and crabs; and dwarf angels (coral beauty, flame) may nip clams or LPS. Each fish's care guide states its exact caveat.
What fish are good for a nano reef tank?
In a small tank (roughly 20 gallons or less), stick to the small, peaceful fish: banggai cardinalfish, bicolor blenny, firefish goby, green clown goby, neon goby, ocellaris clownfish, orchid dottyback, pajama cardinalfish. Avoid tangs, dwarf angels and large wrasses — they need 55–125 gal. Even in a nano, keep one territorial fish of each kind, and add the pushier fish last.