Freshwater fish compatibility checker for aquarium planning
Not every fish that fits in a tank belongs in that tank.
TanksConnected helps fishkeepers think about compatibility before problems start: size, temperament, territory, water needs and long-term stocking.
This public page explains the feature. Create a free account to save your own tanks, add livestock, record test results, and keep your aquarium history together inside TanksConnected.
Compatibility factors
- Compare fish against tank size.
- Think about aggression and temperament.
- Consider adult size and predation risk.
- Plan stocking groups and territories.
- Keep notes on behaviour over time.
Size compatibility
Fish need to be judged by adult size, body shape and mouth size, not just how harmless they look in the shop.
Temperament compatibility
Peaceful, semi-aggressive and territorial fish need different stocking plans and escape space.
Water compatibility
Temperature, pH and hardness ranges should overlap enough for all fish to thrive long term.
Avoid the classic stocking headache
Compatibility mistakes are expensive and stressful. TanksConnected gives you a place to plan, review and adjust before the fish are already fighting.
Frequently asked questions
What makes freshwater fish compatible?
Freshwater fish compatibility depends on adult size, temperament, territory needs, water temperature, pH, hardness, group size and whether one fish could bully or eat another.
Can peaceful fish still be incompatible?
Yes. Peaceful fish can still be incompatible if they need different water conditions, different temperatures, very different tank sizes or if one species is small enough to be eaten.
Why does adult fish size matter for compatibility?
Adult size matters because many fish are sold small but grow much larger. A fish that seems safe in the shop may become territorial, predatory or too large for the tank later.
Should compatibility be checked before buying fish?
Yes. Checking compatibility before buying fish is far safer than trying to fix aggression, stress or water quality problems after the fish are already in the aquarium.