Re:Hello – Looking seriously into Seahorses!

Pete Giwojna

Dear RJ:

Sexy shrimp (Thor amboinensis) are colorful and their dancing is entertaining to watch. They are peaceful and get along together in groups or colonies. They are seahorse safe but I would fear for their safety in an aquarium with large seahorses. They are pretty small for shrimp — most specimens I have seen range from about 1/4 to 1/2 inch in length — and that makes them fair game for hungry seahorses.

Remember, live shrimp are the favorite food of all seahorses and, up to a certain point, they will not hesitate to attack shrimp that are too large to be eaten in one bite.

This often happens when feeding seahorses live ghost shrimp or grass shrimp, many of which are too big to be eaten intact. Seahorses are so fond of these shrimp that they often attack specimens that are far too big to swallow. In that case, they will attempt to break the back of the shrimp by snapping repeatedly at the carapace. If they are successful in severing the abdomen from the cephalothorax, the seahorses will then slurp up the tail section and head half of the shrimp separately. Or should their victim be so large it cannot even be swallowed in sections, they will snick out mouthfuls of the soft tissue exposed inside the abdomen or thorax.

At times, several seahorses will gang up on one big shrimp this way, like a pack of lions teaming up to bring down a water buffalo that’s too big for any one of them to tackle alone. Under the right circumstances, a sort of slow-motion feeding frenzy may then ensue, with the seahorses playing tug-of-war over the pieces of their prize.

Grass shrimp that are too large to be overcome by such tactics may survive to become long-term residents of the seahorse tank, coexisting with their reluctant tankmates in a sort of uneasy truce. Such die-hard shrimp provide a useful service as scavengers from then on.

In short, I would be concerned that large seahorses would regard your sexy shrimp as tasty snacks. You might be better off selecting one of the larger varieties of decorative shrimp instead. For example, large Peppermint Shrimp (Lysmata wurdemanni) and/or Scarlet Cleaner Shrimp or Skunk Cleaner Shrimp (Lysmata amboinensis) would complement your cleanup crew and add a touch of color and activity to the tank.

Otherwise, the proposed seahorse tank you are planning sounds just fine. A 45-gallon aquarium that is 24 inches tall will provide the height and stability you need and provide a comfortable margin of error for a first-time seahorse keeper. (You could probably get by with a 30-gallon Extra-High All-Glass Aquarium, which is also 24 inches tall, just fine providing you were diligent about maintenance and willing to limit yourself to fewer seahorses, but the 45-gallon setup is a better choice and will definitely provide you with a bigger margin for error. When the time comes and you need to move the aquarium to a new location, just let me know and I’ll provide you with some suggestions that will make the move much easier.

A bio-wheel provides basically the same benefits as a wet/dry trickle filter and is less expensive. A combination of live rock to provide the bulk of the nitrification and denitrification for the aquarium, supplemented by a biowheel, protein skimmer, and an ultraviolet sterilizer, will provide the basis for an efficient filtration system.

However, you won’t need anything near 5 pounds of live rock per gallon. Even in systems where the live rock is the only means of biofiltration, 1-2 pounds of live rock per gallon is all that is required. The biowheel in your tank will provide plenty of biofiltration all by itself, so you should certainly be able to get by with less than 1 pound of live rock per gallon. Look for pre-cured live rock with interesting formations that are heavily overgrown with pinkish and purplish coraline algae.

If you would like to get a dark colored sand for your substrate, which I also prefer, rather than whites sand or gravel, there are a number of good options you can consider. I find that a fine-grained oolitic live sand, preferably black, helps control nitrates and looks great, as discussed below.

A thin layer of live sand is the ideal substrate for a seahorse tank. It is bioactive, aesthetically pleasing, and is a fine-grained sand well suited for the various snails that form an essential part of the cleanup crew for a seahorse tank. I find the dark color of an oolitic black sand substrate shows off my seahorses and macroalgae to great effect and enhances the appearance of tank in general.

As long as it’s fine enough I’ve never had any problems with seahorses "snicking" up sand in the aquarium. They will do so on occasion when feeding off the bottom, but never have any difficulty at all expelling it again as long as it’s fine grained. So I find that very fine "sugar" sand works for a well for seahorses, and you don’t have to worry about any pebbles or bits of rock that are too large to be accidentally ingested. What is sometimes problematic are small pebbles or bits of rock that might be accidentally slurped up a seahorse’s tube snout when they are feeding on the bottom, and which could then be difficult for the seahorse to expel again.

The depth of a shallow sand bed like this is also an important factor. Too deep, and you risk anaerobic dead spots where deadly hydrogen sulfide gas can form. Too shallow, and there will be less surface area to support beneficial nitrifying bacteria and Nassarius snails and other beneficial burrowers may feel vulnerable and exposed. A bed of live sand between 1/2 to nomore than 1-inch deep is just right for the main tank. A properly layered Deep Live Sand Bed (DLSB) 3-6 inches deep with a full complement of sand shifters also works well with seahorses, but is best confined to a sump rather than the display tank due to the seahorse’s heavy waste production. In other words, you can minimize the buildup of detritus in the DLSB by installing it in your sump rather than the main tank.

The types of live sand I prefer are either the Arag-Alive Indo-Pacific Black Sand by CaribSea or else the CaribSea Tropical Isle Tahitian Moon Black Sand. You can obtain them online from Premium Aquatics and a number of other sources, and either of them should work well for the substrate in a seahorse tank.

As you know, RJ, a refugium is simply a self-contained protected area, isolated from the main tank but sharing the same water supply, which provides many of the same benefits as a sump. A refugium can help newly added fish or invertebrates easily acclimate to a new tank. It can provide a safe haven for injured fish or corals to regenerate damaged tissue without the need for a separate quarantine tank. But perhaps its main benefit for the seahorse keeper is provide a protected area where macroalgae can be grown and small live prey items (copepods, amphipods, Caprellids, etc.) that will eventually become a food source for the inhabitants of the main portion of the tank can be cultured safely, allowing their population to build up undisturbed.

For instance, Charles Delbeek likes to use glass shrimp and cleaner shrimp that are too large to be eaten in the refugium for his seahorse tank, where the regular reproduction of these hermaphroditic crustaceans will provide a continuous supply of nutritious nauplii for his ponies: "There is a method that can be used to offer an occasional supply of live food for your sea horses. By setting up a separate system housing several species of shrimp such as the common cleaner shrimp, Lysmata amboinensis, or Rhynchocinetes uritai or R. durbanensis, you can get a fairly regular supply of live shrimp larvae. These species are best to use since they can live in large groups and spawn on a regular basis. Such a system is commonly called a refugium. A refugium is a small (10-20 gallon) aquarium that contains live sand, live rock and/or macroalgae such as Caulerpa. It is plumbed such that water from your main system is pumped to the refugium and then returns via an overflow to the main tank. For this type of arrangement to work, the refugium must be slightly higher than the main tank. Shrimp are added to the refugium and within a few months they should start spawning and hatching eggs every few weeks. The larvae are then carried back to the main tank by the overflow, where they become a food source for your sea horses. Of course other life will also thrive in the refugium and it is not unusual for copepods, mysis and crab larvae to also be produced on a regular basis. The key to the refugium is to keep predators out of the system so that the smaller micro-crustacean population can thrive. You would need a fairly large and productive refugium to produce enough food to maintain even a pair of sea horses, so at best, a typical refugium can provide a nice source of supplemental live food; the basic daily diet still needs to be provided by you in the form of the frozen foods mentioned above." (Delbeek, November 2001, "Horse Forum," FAMA magazine)

Aside from the one Delbeek favors, refugia are available in a number of different designs and all different sizes. For example, there are easy-to-install external hang-on refugia and in-tank refugia as well as sump-style refugia that are mounted beneath the main. In the case of the latter, the refugium is installed exactly like any other sump. Here are a couple of online sites where you can look up more information on refugia, including articles explaining how to set up and install a refugium of your own:

Click here: Refugium Setups Information – From About Saltwater Aquariums

Click here: Refugiums

best of luck finding just the right refugee him for your new seahorse tank, RJ!

Pete Giwojna

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