- Temperature: Seahorses are ectothermic, which means that their body temperature is regulated by the environment. They are most active in warm waters, and their range is limited by the temperature of their habitat.
- Salinity: Seahorses are found in a variety of salinities, but they prefer waters that are near the salinity of seawater. They are able to tolerate some variation in salinity, but they can be stressed or killed by sudden changes in salinity.
- pH: Seahorses prefer waters that are near neutral pH. They can tolerate slight variations in pH, but they can be stressed or killed by sudden changes in pH.
- Oxygen levels: Seahorses require high levels of oxygen in the water. They are able to tolerate low oxygen levels for short periods of time, but they can be stressed or killed by prolonged exposure to low oxygen levels.
- Light: Seahorses are most active during the day, but they can also be found at night. They prefer well-lit habitats, but they can tolerate some darkness.
- Substrate: Seahorses anchor themselves to the substrate using their tail. They prefer substrates that are dense and provide good support, such as coral rubble, seagrass beds, and macroalgae.
- Pollution: Seahorses are sensitive to pollution, and they can be harmed by pollutants such as oil spills, sewage, and plastics.