Without knowing more about your aquarium system, two things occur to me offhand that often account for adverse color changes in seahorses.
First of all, one reason brightly colored seahorses may darken in a new aquarium is if the lighting is too intense. In nature, bright light means exposure to harmful ultraviolet radiation, and the seahorses respond by producing excess melanin, just as people will develop a dark tan in the summertime if they spend a lot of time in the sun. For this reason, seahorses that are displayed under metal halide lighting or other high intensity lighting may darken in coloration due to the excessive production of melanin. As Jorge Gomezjurado (Head Curator at the National Aquarium in Baltimore and the founder of Draco Marine) reports, “I have exposed yellow seahorses to strong metal halide and they have turned black in few hours.” It would be a terrible shame to display colorful seahorses such as Sunbursts or Fire Reds or SunFires under metal halides or other high-intensity lighting, only to see them darken in coloration and lose their vivid colors…
On the other hand, the proper lighting can often greatly enhance the appearance of colorful seahorses. When it comes to the lighting system, be sure to avoid high-intensity lighting such as metal halides, or even high-intensity LEDs designed for use in reef tanks, which will have a detrimental effect on the coloration of brightly colored seahorses. In order to display Fire Reds and Sunbursts in their orange color phase to best effect, keep the following suggestions in mind in that regard:
For general purposes, most seahorse keepers would do well to consider the lighting system that Paul Groves prefers for bringing out the best colors in his Hippocampus subelongatus seahorses, which display a wide range of coloration, including yellow and orange color phases. Paul Groves, curator at Underwater World in Perth, recommends combining a triphosphor (6500k) fluorescent tube with a Phillips TL Blue fluorescent tube to produce the best overall lighting for a seahorse exhibit. After much experimentation, he found the above combination of lights really encouraged the coloration of the seahorses as well as being aesthetically pleasing to the eye. He reports that the diversity in colors displayed by Hippocampus subelongatus was much less under any other lighting. So if you want to bring out the brightest colors in most seahorses, try a 6500k triphosphor fluorescent in conjunction with a Phillips TL Blue fluorescent to keep them looking their best. Avoid metal halide lighting and other high-intensity lighting for your seahorse tank.
The West Australian Seahorse (Hippocampus subelongatus) is a very handsome species that is often pale but also displays a wide range of bright colors, including yellow, orange, red, pink, purple, black and white (Bull and Mitchell, 2002, p53). Michael Payne reports that coloration appears to be sex-linked in this species with the red and pink specimens typically being males while the yellow individuals are almost always females (Bull and Mitchell, 2002, p53). A narrow band of brown typically encircles the spines. In addition, some specimens are further adorned with a reticulated pattern of fine lines. All H. subelongatus display the attractive trademark striped snout (Bull and Mitchell, 2002, p53), which gives this species the alternate common name of the Tigersnout Seahorse. So I am thinking that the lighting system that produce the best results and brightest colors for Paul Grove’s H. subelongatus would also be an option home hobbyist can consider for Fire Reds or bright yellow Sunbursts.
But for best results, if you obtain bright orange or red seahorses, then I strongly urge you to consider adding one or more Aqueon ColorMax florescent tubes or Gro-lux fluorescent tubes to your aquarium reflector. Osram Gro-lux bulbs and Aqueon ColorMax fluorescents put out wavelengths of light that are concentrated toward the red, orange, and violet regions of the spectrum. They are intended to stimulate better plant growth, but have the added effect of greatly enhancing any red or orange or purple colors they illuminate. When bathed in ColorMax or Gro-lux light, bright orange or red seahorses literally glow!
Osram Gro-Lux florescent tubes are designed to stimulate plant growth, so look for them in nurseries, garden centers, and horticultural supply outlets rather than in fish stores or pet shops. In short, if you want to accent the colors of orange, red, or purple seahorses, Osram Gro-lux fluorescents and Aqueon ColorMax fluorescents are ideal; for other seahorses, try a 6500k triphosphor fluorescent in conjunction with a Phillips TL Blue fluorescent to keep them looking their best.
NOTE: Osram Gro-Lux florescent tubes may be difficult to locate and some parts of the country, but I am happy to report that the Aqueon ColorMax fluorescent bulbs designed for aquarium use will have the same dazzling effect on red and orange seahorses, and the ColorMax lights are readily available from pet shops and aquarium stores.
If the lighting is not the problem in this case, then it could be that the rock work in your aquarium maybe having an adverse effect on the coloration of the seahorses. If you have a lot of rock work in your aquarium that is the same color (e.g., grayish or shades of brown), then the primary color in your seahorse setup may be brown or gray, in which case the seahorses may have adopted similar drab coloration in order to make themselves less conspicuous and blend in better with their background.
I will send you an e-mail with a document attached that is devoted to the subject of aquascaping your aquarium to encourage your seahorses to look their best and brightest at all times, so that you can download the document, save it on your computer, and read through the information at your convenience. You may find it has some useful suggestions for helping restore your seahorses to their true glory.
Pete Giwojna, Ocean Rider Tech Support