Freshwater Fish Compatibility Tool
Pick up to 5 species and get instant compatibility, water-parameter overlap, tank-size tips, and stocking notes.
Accuracy note: This tool uses expert rules + smart checks (biotope, temperament, size, water). Individual behavior varies. Always observe, quarantine, and avoid overcrowding.
Quick compare:
Usually compatible
Sometimes compatible
Rarely compatible
Other potentially compatible fish
Tank & Water Guidance
Water parameter overlap
Minimum tank advice
Stocking & behavior tips
Important: Brackish vs freshwater/coldwater mismatches are marked Rarely. Size predation risk is considered. Avoid mixing African rift-lake cichlids with South American community fish. Always quarantine new fish for 2–4 weeks.
Fish Compatibility Chart: How to Read & Use It
Use the compatibility checker above to compare up to five species. This guide explains how to read the fish compatibility chart, what the colors mean, and simple rules for what fish can go together in a peaceful, healthy aquarium.
How to Use the Compatibility Checker
- Select up to 5 species in the dropdowns above.
- Read the matrix colors for each pair (Usually / Sometimes / Rarely).
- Review the Water Overlap (temperature & pH), Tank Advice, and Stocking Tips cards.
- Use Other Potentially Compatible Fish to expand your community list.
- Save your plan with the shareable link (Copy link button).
Tip: If any pair shows Rarely Compatible, pick an alternative from the suggestions instead of forcing a risky mix.
What the Colors Mean
Usually Compatible
Sometimes Compatible
Rarely Compatible
- Usually Compatible — Safe in most community setups when tank size and water overlap are met.
- Sometimes Compatible — Case-by-case. Watch group sizes, aquascape, feeding zones, and territory.
- Rarely Compatible — High risk due to water type mismatch, aggression, or size/predation concerns.
Simple Rules for What Fish Can Go Together
Match Water Type
Keep tropical, coldwater, and brackish setups separate. Mixed water types are flagged in the chart.
Balance Temperament
Pair peaceful with peaceful. Nippy or territorial species increase risk and push pairs into “Sometimes” or “Rarely”.
Consider Adult Size
Large mouths + tiny tankmates = predation risk. The checker accounts for typical size gaps.
Schooling Numbers
Many community species behave best in proper groups. Bigger groups reduce chasing and stress.
Shared Water Window
Look for a safe overlap in temperature and pH using the Water Overlap card under the chart.
Layout Matters
Provide plants, hardscape, and line-of-sight breaks. Territory and cover often move a pair from “Sometimes” to “Usually”.
What Fish Can Go with GloFish?
GloFish are fluorescent versions of common species. Compatibility follows the original species’ behavior, water needs, and adult size. In the checker, select the base species (for example, “danio”, “barb”, or “tetra”) and build your plan from there.
- Keep each type in appropriate groups to spread attention and reduce nipping.
- Pair with species that share the same water type and have overlapping temperature/pH ranges.
- Avoid slow, long-fin tankmates with active or nippy fish. If the chart shows “Sometimes” or “Rarely”, pick another option.
FAQs: What Fish Can Go Together?
How accurate is the fish compatibility chart?
The chart combines expert rules with smart checks for water type, size differences, and typical behavior.
Individual fish vary, so always observe, quarantine new arrivals, and avoid overcrowding.
What if two species show “Sometimes Compatible”?
“Sometimes” means it depends on tank size, numbers, aquascape, and feeding zones. Increase group sizes, add cover, and
ensure a safe temperature/pH overlap. If issues persist, choose an alternative from the suggestions under the checker.
Can I mix tropical with coldwater or brackish fish?
No. Keep tropical, coldwater, and brackish setups separate. The chart flags these pairs as “Rarely Compatible”.
Do I need to match fish by region or biotope?
It helps. Species from similar regions often share water chemistry and behavior patterns. Matching biotopes usually improves compatibility scores.
Build a Peaceful Community
Use the checker above, follow the rules here, and adjust group sizes and aquascape. When in doubt, choose from the suggested compatible species.
