It is difficult to say what is going on with your seahorse without having a photograph or anything to go by, but I can tell you that turning green along the backbone or dorsal surface of the seahorse is not a symptom of any disease or any sort of health problem that I am familiar with…
For this reason, I suspect the color change is perfectly normal and, as long as all of your water quality parameters look good and the seahorses eating well and behaving normally otherwise, that I don’t think there’s any reason for you to be concerned about this color change.
For example, such color changes are often seen in tropical seahorses when they are performing courtship displays. It is common for the body of the seahorse to brighten or lighten up in coloration during courtship and breeding activities, with the exception of the head and dorsal surface (i.e. backbone), which typically darken in contrast.
Or the greenish coloration could be due to algae growing on the exoskeleton of the seahorse. Such algae growth is most common on the head of the seahorse and the back of its neck, and down the dorsal surface of the seahorse, which are the areas that review usually receive the most light, as discussed below in more detail:
Algae often grows on the exoskeleton of seahorses, typically on their head and neck which are closest to the light source, particularly when they are kept in reef tanks with high-intensity lighting. In most cases, that’s perfectly normal and nothing at all to be concerned about. Seahorses often encourage algae to grow on them as a protective device to enhance their camouflage, and it’s often best simply to ignore any such growth.
We are all well aware that seahorses can change color to blend into their backgrounds, and that Hippocampus is capable of growing or shedding dermal cirri, which are long filaments and branching extensions of its skin, as called for in order to match its immediate environment. To complete its disguise, the seahorse allows algae, bryozoans, hydroids, and other encrusting organisms to grow on its body, thereby rendering it all but invisible in its natural habitat. In fact, its skin contains polysaccharides which are believed to encourage algal growth, thereby helping it disappear into its surroundings. This vanishing act is so convincing that, even when they are collected by hand seining, seahorses often go undetected amidst the plant matter that accumulates in the net. Unless the collector is really diligent, he will lose a large proportion of his catch simply because many specimens will be overlooked and thrown back with the debris. In other words, it’s perfectly normal for algae to grow on seahorses.
If you can show me one or more good photographs of your seahorse that show it’s backbone clearly, that will give me a much better idea of what you’re talking about and I will be able to give you better advice regarding whether or not the change you’ve noticed is normal.
You can reach me at the following e-mail address anytime:
In the meantime, just be sure to maintain optimum water quality and make sure that your seahorse is behaving normally otherwise.
Best wishes with all your fishes!
Pete Giwojna, Ocean Rider Tech Support