Sea Lettuce

Dear Joe:

Yes, sir, the Hawaiian volcano shrimp certainly do like Ulva sea lettuce as well as other forms of algae. If some of the leaves of the sea lettuce have turned white, that’s usually an indication that they are not getting enough light. The whitening is caused by the loss of the chloroplasts that convert sunlight into food for the sea lettuce via photosynthesis. We often see that sort of blanching when live plants are shipped through the mail. After several days of complete.darkness in the shipping box, the plants may turn white due to the lack of sunlight. When that happens, the plants normally green up again quickly when they are provided with sufficient light and remain perfectly healthy. So the leaves of your sea lettuce that have turned white are not dead and should not be removed. Try giving them more light and see how they respond. They should be getting at least 12 hours of light each day, which the red volcano shrimp won’t mind at all. (You want to encourage algae growth in the aquarium that houses the shrimp.)

Ulva sea lettuce is found in shallow water and is accustomed to fairly bright light, which gives it its characteristic light green to dark green coloration. The translucent leaves are only two cells thick, which helps the chloroplasts to better absorb sunlight. They should be green up again nicely when they are receiving adequate light.

Otherwise, it sounds like you set up a very nice home for the red feeder shrimp, Joe. You will find the red feeder shrimp (Halocaridina rubra) to be easy to keep and relatively undemanding to culture, although their numbers build up very gradually due to their naturally slow rate of reproduction.

Red feeder shrimp or volcano shrimp, as they are sometimes known, prefer brackish conditions and breed best at reduced salinity (1.0145-1.0168) but they adapt well to full strength saltwater and will survive indefinitely is a marine aquarium. They are a perfect "feed-and-forget" treat for large seahorses! As a rule they don’t need a great deal of room. A simple sponge filter will do. The Care Sheet for the volcano shrimp is available online at the following URL:

http://www.seahorse.com/Aquarium_Life/Care_Sheets/Red_Shrimp/

Here is some additional information about these shrimp, including suggestions for feeding them, that may be of interest to those of you who are interested in keeping or culturing these colorful little crustaceans:

RED FEEDER SHRIMP from Hawaii (Halocaridina rubra)

Pros:

* Excellent nutritional value

* Irresistible to all the greater seahorses.

* Feed-and-Forget — lasts forever in saltwater!

* Easy to enrich.

* Simple to gut-load.

* Can be cultured using simple techniques and the most basic setups.

Cons:

* Reproduces slowly; difficult to build up a large population.

Collecting Tips:

None.

Culture Instructions:

Specific gravity: 1.0145-1.0168; pH: 8.0-8.3

Temperature: 68° F – 73° F (20° C – 23° C)

These fabulous little feeder shrimp can be kept indefinitely in a spare 2-10 gallon tank, or even a clean, plastic bucket, that has been filled with clean saltwater and equipped with an airstone for aeration. Neither a heater nor a fancy filtration system is required. They thrive at room temp and reduced salinity (1.015-1.016), and all they require is an airstone (or a simple air-operated foam filter at most) to keep the water oxygenated, with perhaps a little coral rubble as substrate and a clump or two of macroalgae (sea lettuce, Ogo, Gracilaria) to shelter in. They’re easy to feed — they feed primarily on algal mats and bacteria — but they will accept vegetable-based flake foods and pellets such as various Spirulina products. They are filter feeders and can also be fed with yeast or commercially prepared foods for filter-feeding invertebrates. Many people find an easy way to feed them is to place a small piece of algae-encrusted live rock in their holding tank; once they clean it off, simply replace it with a new piece of algae rock. But if you want to culture them, I’d recommend ordering the special shrimp food formulated just for them when you order your feeder shrimp from Hawaii. It’s called Shrimpgro and is designed to meet all their needs and requirements:

http://seahorse.com/shop/index.php?main_page=product_info&cPath=2&products_id=6

Comments:

These tiny red feeder shrimp (Halocaridina rubra) are native to Hawaii where they inhabit underground lava tubes. Brackish pools collect in the cracks, crevices and depressions in the lava below the water table, thus forming the habitat for the shrimp. The brackish water that fills these pools consists of intrusive seawater diluted by freshwater that percolates downward. Because of their lava-tube habit, they are sometimes called Hawaiian Volcano Shrimp.

Native Hawaiians call them Opa’e-ula, and they are unique among the several different species anchialine pond shrimp in being small, social, herbivorous shrimp that feed mainly on algae and bacteria. They are known to feed on insects that drown in the lava tubes. When conditions are favorable, they may feed en masse at the surface in swarms of countless individuals that turn the water red.

Halocaridina rubra look like miniature, bite-size Peppermint Shrimp, and all seahorses save the miniature species go absolutely nuts for them! They are very nutritious and eat a varied, omnivorous diet. They are perfect for seahorses in every way.

Unfortunately, it is very difficult to culture these shrimp in any quantity, since they reproduce slowly and the females only carry 12 to 14 eggs. They spawn but 4 or 5 times and produce an average of only 5-10 larvae per spawn. The larvae hatch as free-swimming, yolked zoeae after a brooding period of 38 days. Larval development is abbreviated with four zoeal stages and one megalopial stage occurring before they reach the first juvenile stage. Duration of the larval stages in the aquarium is 24 to 27 days at 22 to 23 degrees C.

Like other shrimp, it is the complicated larval developmental period they undergo, with multiple zoea and megalops stages, that makes the larvae difficult to raise, Joe. However, it can be accomplished the same way other decorative shrimp such as peppermint shrimp (Lysmata wurdemanni) are raised. There is a very interesting and informative book that explains exactly how to go about raising such shrimp that I recommend you read. It’s called "How To Raise & Train Your Peppermint Shrimp" by April Kirkendoll and they can be obtained at the following URL:

http://saltaquarium.about.com/cs/fprswaqbooks/fr/aafprpshrimpboo.htm

You’ll find lots of excellent information on raising peppermint shrimp in April’s book that will apply equally well to your volcano shrimp.

Best of luck culturing your red feeder shrimp, Big Joe!

Happy Trails!
Pete Giwojna