Dear Haynes:
Your lighting should be fined as long as you provide your seahorses with some shaded areas and 190 W does not overheat your 30-gallon aquarium, as discussed below:
When ut comes to lighting, seahorses do not have any special requirements other than the fact that most species prefer low to moderate light levels rather than excessively bright light. They have a corrugated retina especially rich in rods, which gives them excellent visual acuity under twilight conditions and low light levels in general. But this does not mean that they shun bright light, just that they appreciate shady retreats as well as brightly illuminated areas.
In actual practice, seahorses will do well under any type of lighting you prefer — from metal halides to power compacts or VHO lighting to daylight fluorescent tubes to ambient room light — providing shaded areas are available to them and overheating does not become a problem.
In fact, Hippocampus is often displayed under metal halide lighting at public aquaria(Seahorse Husbandry Manual, 2002). For example, the 2002 Seahorse Husbandry Manual indicates that metal halide lighting is often the preferred choice for displaying Hippocampus erectus at such facilities, and this applies to other species as well. Brian Zimmerman and Heather Hall maintain a very successful breeding program for H. capensis at the London Zoo, with the main tank being illuminated for 11 hours a day by 2 HQI metal halides (150 watts each, 10,000 Kelvin). Karen Brittain also kept H. fisheri at Waikiki Aquarium under metal halide lighting with a natural photoperiod. Likewise, Jorge Gomezjurado reports that he has kept adult H. ingens and H. reidi on display at the National Aquarium in Baltimore under Metal Halides Lamps (175W 6500K) that provided a photoperiod of 12:12 L:D without any problems.
So your metal halides would be considered overkill by most seahorse keepers, and not my first choice, but the pros often use them and I know many reef keepers who keep seahorses in their systems under metal halides. Often the reefers will keep the coral and inverts that require strong light at one end of the tank, where the metal halides are concentrated, and keep the other of the tank shaded to accommodate the seahorses, reserved for coral that don’t need high-intensity lights. Basically, you can’t go wrong with seahorses when it comes to lighting as long as you provide some dimly lit areas they can retreat to when they would like to get away from the light and some brightly lit areas they can move to when then want to bask in the light. If you’re using metal halides, you can provide shaded areas by positioning sections of aluminum foil atop your aquarium that are the right size and shape to cast shadows where you want them below.
In short, my primary concern when using high-intensity lighting such as metal halides on a seahorse tank is the water temperature rather than the brightness of the light. Metal halides throw off a lot of heat and most of the tropical seahorses do best at temperatures of around 73°F-75°F; so avoiding temperature spikes above 80°F is very important. If your metal halides consistently keep your reef system at 78-80°F, stick to seahorses that prefer warmer water temperatures, such as H. barbouri or H. kuda.
Personally, I like to provide my seahorses with a natural day/night period that includes twilight periods at "sunrise" and "sunset." To accomplish this, I like the power compact (PC) light fixtures that include two tubes — one actinic and one daylight fluorescent — with dual ballasts so that each ballast can be placed on a separate automatic timer. I like to have the bluish actinic come on before the daylight tubes and stay on after the daylights go off, thereby providing a simulated dusk and dawn (Giwojna, unpublished text). This is important for seahorses since they conduct most of their courting and breeding in the early morning hours under twilight conditions. It’s a neat effect and fish and invertebrates can then anticipate "lights out" rather than being plunged into total darkness at night or suddenly thrust into bright light in the morning. I also adjust the timers to lengthen or shorten the daylight periods in accordance with the changing seasons. I find that maintaining a natural cycle this way aids reproduction (Giwojna, unpublished text).
Basically, I find PC lighting to be a good compromise for a seahorse system. Power compacts provide plenty of light for macroalgae or the seahorse-safe soft corals in a modified reef system without being too bright or generating too much heat, and the dual ballast system allows for a natural day/night rhythm that changes with the seasons. The resulting dusk and dawn facilitate courtship and help the seahorses maintain a natural reproductive cycle (Giwojna, unpublished text).
For all intents and purposes, you really can’t go wrong no matter what lighting system you chose as long as you provide both shaded areas where your seahorses can escape from light altogether and well-lit areas where they can bathe in bright light as they please. You will find your seahorses will move into and out of the light often, seeking the comfort level that suits them at the moment.
Best wishes with all your fishes, Haynes!
Happy Trails!
Pete Giwojna
Ocean Rider, Inc. is an Organic Hawaiian-Based Seahorse Aqua-Farm & Aquarium that Follows Strict Good Farming Practices in Raising Seahorses and Other Aquatic Life.
