Seahorse Frequently Asked Questions / Does water temperature effect sea horses?
Yes. Seahorses come from seas ranging from temperate (cold water) to tropical (warm water). If a species from temperate waters is exposed to excessively warm water, they become stressed, possibly to the point of being fatal. This is one reason climate change is a threat to seahorses. One additional problem is that the warming of ocean temperatures appears to be causing warm water species to invade territories they never have before, competing with the native seahorses. For instances, there is record of Hippocampus algiricus being found around the Canary Islands for the first time, and cross breeding with the native Hippocampus hippocampus.
Cold water can have the same effect on tropical seahorses. Water that is too cold can stress tropical seahorses and too cold can kill them. Water that one species is perfectly happy in can be fatally too cold for other species.
In the home aquarium, temperature is also very important. Seahorses have a primitive immune system, which makes them very susceptible to bacterial diseases. In the wild, or even systems with large volumes and relatively low bioloads (the number of animals in a system), bacteria counts stay low. But in a home aquarium, bacteria tend to occur in much larger numbers. For years, people tried to understand why their seahorses were getting sick so frequently. In warmer water, bacteria reproduce at faster rates. The warmer the water, the faster bacteria reproduce. Seahorses are more prone to become ill do to overwhelming numbers of bacteria, especially when stressed, while other fish, because of their more advanced immune systems, are better equipped to deal with bacterial illness so they don’t get sick as often.
What aquarists have found is that turning the temperature down a few degrees from what they would experience in the wild. While it is only a hypothesis, the practice of keeping seahorses at temperatures slightly lower than they might be found in the wild has significantly reduced the amount of illness seahorses in captivity experience.
You can read more about temperature and seahorses in the aquarium here.