Pete Giwojna

Dear Tammy:

Yes, that’s correct – the type of lighting used for your seahorse tank is not a critical factor, and they will do equally well under most types of lighting, with a couple of exceptions we will discuss in more detail later in this message.

In fact, Tammy, it is the photoperiod or duration of the lighting that is more important than the type of lighting you use, and you can indeed influence the breeding behavior of your seahorses by adjusting the lighting properly. Manipulating the photoperiod of your seahorse tank can affect courtship and mating in two ways.

First of all, adjusting the lighting to provide the seahorses with a simulated dusk and dawn gives them more natural conditions that are conducive to breeding. In the wild, most of the interactions between mated pairs are conducted during the twilight conditions following first light at the crack of dawn, including morning greetings and the various courtship displays that lead up to the transfer of the eggs at the climax of the proceedings. This is also true of the highly domesticated Ocean Rider seahorses which are raised under natural sunlight at the seahorse farm in Hawaii. The seahorses at the aquaculture facility therefore experience a normal dusk and dawn just as they would in the wild, and the daily and lunar light cycles certainly influence mating and the timing of their breeding activities.

For instance, parturition in gravid males is a good example of how the dark/light cycles allow the seahorses to coordinate their breeding activities. If you want to witness a pregnant male delivering his brood, this is what Carol Cozzi-Schmarr at Ocean Rider recommends in that regard:

"In my experience, I have seen that 90% of the time the male seahorse will give birth right at the crack of dawn. For example, in one section of our hatchery we have over 50 pairs of seahorses. On any given morning if you show up just before dawn, you will witness at least 5 males giving birth at exactly the same time which is right at dawn. It is spectacular!! So, I would bet that if you set your alarm to 1 hour before sunrise you just might get lucky!! But of course, you will have to ask Mr. Seahorse to be sure!!!"
Aloha, Carol

The point is that providing your seahorses with a simulated dusk and dawn can help to stimulate a healthy interest in courtship and breeding. Providing the twilight periods at dusk and dawn can easily be accomplished with some of the new LED light fixtures which include timers and sometimes even allow you to adjust the intensity of the differently colored LEDs as you wish. Mimicking dusk and dawn is also easily accomplished with lighting fixtures that include both blue actinic tubes as well as normal daylight fluorescent tubes, simply by having the actinic lighting turn on a half hour or so before the regular fluorescent lighting, and adjusting the actinic lighting so that it stays on for half an hour or so after the daylight fluorescents are turned off.

The second way the photoperiod can influence breeding in seahorses is by shortening or lengthening the full light periods to simulate the seasonal changes in the hours of daylight. The level of certain hormones such as gonadotropin, which controls gonadal development, are regulated by the hours of daylight a seahorse receives. For example, Hippocampus erectus breeds best during late spring and summer when the hours of daylight are the longest and stops breeding when the hours of daylight drop below 10 hours daily.

For this reason, if you only leave the aquarium lights on for 6-10 hours or less each day, you may be suppressing courtship and breeding in your seahorses. Likewise, if you increase the hours the aquarium lights are burning to 12 are more, you may stimulate breeding behavior in Mustangs and Sunbursts.

To understand why the photoperiod is so important for regulating breeding, we must first understand how the light-dark cycle regulates the levels of key hormones that control breeding. Gonadotropin (GtH) is a hormone that stimulates the growth and activity of the gonads and thus controls reproductive activity in vertebrates. It is secreted by the pituitary gland and stimulates the growth and function of the ovaries and testes. The levels of gonadotropin in the body are in turn regulated by melatonin, a hormone secreted by the light-sensitive pineal gland in response to darkness. Among a great many other functions, melatonin switches on a recently discovered enzyme known as gonadotropin inhibitory hormone, thus reducing the levels of gonadotropin in the body and shutting down reproduction (Sanders, 2005).

In other words, when the days are shortest and there is less sunlight, melatonin secretion is high and the levels of gonadotropin are reduced accordingly, causing the gonads to shrink and turning off reproduction. Likewise, when the days are longest and there is more sunlight, melatonin secretion is low and the levels of gonadotropin are high, stimulating the gonads and triggering reproductive activity (Sanders, 2005).

Thus, if you deny the seahorses sufficient daylight and keep their aquarium darkened long enough each day, you can shut down the production of key hormones and prevent your seahorses from breeding, Tammy, as explained in more detail below by Steven Young, the Aquarium Biologist at the Seattle Aquarium:

<open quote>
I haven’t altered temp and lighting seasonally but I have done so to control mating behaviour in my erectus. I’ll usually drop temps down to 74 and light cycle to 10 hrs when I don’t want mating. Normal parameters are 78 and 12 hrs. I don’t do much in terms of salinity, but since we do use NSW, we get fluctuations from 26-31ppt depending on rainfall.

Steven Yong
Aquarium Biologist
AZA PMP Leader and Studbook Keeper – Lined Seahorse
Seattle Aquarium
<close quote>

Dwarf seahorses (Hippocampus zosterae) offer another good example of the importance of the proper photoperiod in stimulating mating. The diminutive dwarfs best when the days are longer than 12 hours (Strawn 1953; Strawn 1954; Strawn 1958). They stop breeding altogether when the period between sunrise and sunset is less than 11 hours (Strawn 1953, 1954, and 1958). So you may have literally been turning off your seahorse’s breeding instincts with the flick of a switch if you are in the habit of switching off your aquarium reflector after 6-10 hours each day! Provide your seahorses with a simulated dusk and dawn, and keep your aquarium lighted for 12 hours a day and you can encourage your seahorses to breed.

Here was what I normally advise home hobbyists regarding the lighting for their seahorse setups, Tammy:

Lighting the Seahorse Tank

When it 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. Some species are even believed to be nocturnal (e.g., Hippocampus comes and H. ingens) and have no trouble seeing and feeding at night. Seahorses will do just fine under ambient room light with no aquarium light fixture whatsoever, although hobbyists prefer to keep their tanks illuminated for aesthetic purposes and so they can view them better.

But this does not mean that seahorses shun bright light (far from it), just that they appreciate shady retreats as well as brightly illuminated areas. However, it’s generally best to avoid high-intensity lights such as metal halides for a seahorse tank. In addition to providing high-intensity lighting, the metal halides also tend to generate a lot of heat, and heat stress can be very detrimental to seahorses. In addition, seahorses don’t like excessively bright light and they may go into hiding, seeking shaded areas amidst the rockwork, if the lighting is too intense for their comfort level. And the seahorses won’t look their best and brightest under metal halides because they will produce excess melanin (black pigment) in order to protect themselves against the harmful ultraviolet radiation they associate with intense light, and darken as a result. For instance, Jorge Gomezjurado reports "…I have exposed yellow seahorses to strong metal halide and they have turned black in few hours." So it would be a shame to display brightly colored seahorses under metal halide lighting in a small, close system aquarium.

Power Compact Lighting

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).

In short, 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).

LED Lighting

Although they are very costly, the new Solaris LED Illumination Systems are another good option for a seahorse reef. The Solaris LEDs can provide the spectrum of light and intensity needed by light-loving corals without the same concerns regarding overheating that make metal halides undesirable, and that’s a huge plus for the seahorse keeper. Aside from generating less heat, they also provide very considerable energy savings and the longevity of the LED is also superior to metal halide lamps. Best of all, the flexibility and adjustability of the Solaris LED Illumination System allows you to independently set the lights to duplicate sunrise, daylight, cloud cover, sunset, and even the lunar cycle. They certainly are very expensive, but they have some wonderful advantages over the conventional metal halide lighting, particularly for seahorses. However, because of the cost factor, I prefer PC lighting for a seahorse tank with live corals myself.

Nowadays, Marineland offers a couple of much less expensive LED lighting systems that are well worth the cost: the Marineland Double Bright LED and the Marineland Reef Capable LED. Either of the Marineland LED light fixtures mentioned above would be terrific choices for a seahorse tank. Overheating should not be a problem with either fixture and you should notice an immediate difference in your electrical bills when you replace your metal halides with one of the Marineland LEDs.

Marineland LED Aquarium Lights have a double row of 6K LED Daylight bulbs and a single center row of 60mw Blue LED’s. This type of lighting is very efficient and uses less energy than other types of aquarium lights. More importantly, the LED lights give off very little heat, thereby helping to prevent overheating, which is very important for seahorses. They are economical and very efficient to operate, which means you’ll save on the electrical bill, and they last a very long time, so you’ll also save on replacement costs for the bulbs. The Marineland LED aquarium light fixtures have a single power cord and a single switch that allows either ALL LED’s ON, just the ACTINIC LED’s (for simulated moonlight) or OFF. This allows you to provide your seahorses with a simulated dusk and dawn very easily by simply turning on just the actinic blue LEDs in the morning a half an hour or so before you turn on the LED daylight bulbs, and leaving the actinic blue LEDs on after you turn off the LED daylight bulbs for the night. In short, they are terrific for providing seahorses (and corals) with twilight or low light conditions, full daylight, or total darkness as you wish since they come with a three-mode on/off switch that lets you operate the light fixture in either daylight mode, lunar mode, or the off position with a simple flick of a switch.

I would say that the Marineland Double Bright LED would be perfect for a seahorse only tank or a seahorse tank that will include lush macroalgae and/or a selection of soft corals that don’t require intense lighting. If that is a good match for your plans for the seahorse tank, then I would save the additional money and go with the less expensive Marineland Double Bright LED.

However, if you are thinking of including some of the seahorse-safe SPS corals, which require stronger lighting, then the Marineland Reef Capable LED would be a better choice, if the additional cost is not a big consideration.

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 the 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.

Fluorescent Lighting

As long as you won’t be keeping live corals with your seahorses, an ordinary fluorescent bulb is perfectly adequate for lighting your seahorse tank. Simple fluorescent lights are more than adequate for a seahorse-only aquarium or SHOWLR tank. For such a setup, I would recommend the Aqualife T5 fluorescent aquarium light fixture by Coralife. The light fixtures are available in 20", 30" and 36" lengths to accommodate various aquariums. One 18 W 10K T5 fluorescent lamp should do the job nicely, or you could also get a T5 light fixture that accommodates two bulbs and add an actinic bulb as well. But a single T5 fluorescent lamp should certainly suffice for a fish-only tank. Any well-stocked fish store should carry the Coralife Aqualife T5 fluorescent aquarium light fixtures and provide one for you that suitable for your 30-gallon tank, or you can also order one of them online from a number of sites, including the following vendor:


All things considered, an ordinary incandescent bulb or standard fluorescent tube is normally quite adequate for a seahorse tank. Between the two, I would strongly favor a fluorescent light fixture because they give off less heat (overheating and heat stress can become problems for seahorses during summertime heat waves) and because the fluorescents are more economical to operate. Easier on the old electric bill.

Best of luck working out the perfect photoperiod for your particular ponies, Tammy!

Pete Giwojna, Ocean Rider Tech Support

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