Re:Live shrimp

Pete Giwojna

Dear Erik:

Yes, you want your seahorse to have a well-rounded abdomens at the end of the day when it is well fed. After a good feeding, the seahorses belly rings should be flush or even slightly convex in cross section when viewed from head on. (We never want to see sunken, severely pinched-in abdomens on our seahorses! Concave belly rings are a sure sign of an underfed seahorse, with the sole exception of a female that has just transferred her eggs.)

So if you want to check whether your little Brazilian seahorse (Hippocampus reidi) is eating well or not, don’t look at his profile — just examine him head-on and check out his gut. His abdomen or belly plates should bulge out slightly or at least be flush with his flank, not pinched in or sunken. In other words, when viewed from the back or from head-on, the cross-section of his abdomen should appear concave "( )" or flush "l l" rather than concave ") (" or pinched in.

Live Mysis are the natural prey of seahorses in the wild, so your little H. reidi should go nuts for the bite-size to opossum shrimp you ordered, Erik. If he has been off his feed lately and seems a little thin, but in about 5-10 of the live Mysis at a time and allow them to eat his fill of them each day. (The peppermint shrimp will also find the live Mysis to be tempting, so try to assure that they don’t hog them all. Give them their fill of flake food or something similar before you offer the live Mysis to your H. reidi.

Yeah, you should be able to keep the bulk of the live Mysis going in one of your desktop aquariums providing you can maintain good water quality. They do best on newly hatched brine shrimp (Artemia nauplii), supplemented on flake food made from brine shrimp after they grow a bit. They do eat Cyclop-Eeze, but the frozen form in the big bars usually works best. The powdered Cyclop-Eze might be worth a try though…

There are a number of ways to culture live Mysis, but you’ll find that it’s a fairly challenging, primarily because the life cycle of the Mysis is complicated and the adults are cannibalistic, so you must have a means of separating the larvae.

Here’s an excerpt from my new book on seahorses that discusses the pros and cons of live Mysis, and outlines one method for culturing them that is suitable for the home hobbyist, Erik:

MYSIDS (Opossum Shrimp)

• Excellent food value.
• A favorite natural food that all large seahorses attack greedily.
• Thrives in saltwater: feed and forget — will survive until eaten.
• Can be easily collected at times.
• Cultured Mysis are available.

• Challenging to culture for the home hobbyist.
• Inland hobbyists have no opportunity to collect them.

Collecting Tips:
Mysis shrimp follow a daily rhythm in their movements, regularly forming dense shoals over sandy bottoms or amidst seaweeds, and they can sometimes be collected in vast numbers while shoaling by seining or dragging a large aquarium net through mats of vegetation (Giwojna, Oct. 1996). Look for a shallow, sandy, weedy area at low tide during the day, and you can often see them swimming in the weeds or settling on the sand. If there is a significant current, they will congregate in slack water areas on the down-current side of objects. Once you have spotted a likely location, return at dusk when they are more active and net them as described above (Bentley, 2002).

A large net with very fine mesh works best for collecting mysids. I suggest a net with a mouth at least a foot square and mesh less than 1 mm square (Bentley, 2002).

Likewise, mysids are sometimes concentrated in large numbers in tidal pools on mudflats and grassflats by the falling tide. The stranded Mysis can easily be netted from these pools at low tide.

Culture Instructions (Bentley, 2002):

Specific gravity: 1.016 for estuarine species;
pH: 7.8-8.3 (reproduction stops if the pH falls lower than 7.4);
Photoperiod: 14 hours of daylight provided by two Gro-lux fluorescent tubes.
Temperature: 77 degrees F (25 degrees C)

The following guidelines are based on Maureen Bentley’s methods for culturing Mysis (Bentley, 2002). The main culture tank should be large, well aerated, and heavily filtered. I suggest undergravel filtration in conjunction with external biological filters. Mysids are extremely sensitive to water quality, and a good protein skimmer is vital for this reason (Bentley, 2002). Natural seawater is much preferable to artificial, and if you are using a synthetic mix, it’s best to allow the artificial saltwater to age at least one month before use (Bentley, 2002).

When stocking the main tank, introduce the shrimp gradually until you’ve reached a density of about 20-40 adults per gallon (Bentley, 2002). Overcrowding leads to fighting and dead broodstock. If you notice lots of mysids jumping out of the water, the tank is very likely overstocked (Bentley, 2002).

Small quantities of mysids can be harvested daily using a small glass tank equipped with an air-operated undergravel filter. Place 15 to 20 large gravid females in the small tank, returning them to the main tank as soon as they have released their young (Bentley, 2002). (Mysis are cannibalistic and the young must be separated from the adults.) The young can then be raised in the small tank for a short period.

Feed them newly hatched Artemia nauplii or rotifers twice daily until they are a few days old (Bentley, 2002). After a few days, begin supplementing their feedings with marine flake food on occasion, especially brine shrimp flake food (Bentley, 2002).

A feeding frenzy will follow the introduction of live food, which can help you determine the right amount to feed. When fed the proper amount, this frenzy should last around 15 minutes, during which all the live food should be eaten (Bentley, 2002). You will know you have fed enough when the normally transparent mysids have orange stomachs after feeding on the baby brine shrimp (Bentley, 2002). If the adults — especially the males — start eating numbers of the younger Mysis, that’s a sure sign of underfeeding (Bentley, 2002).

Mysidacea, or Opossum Shrimps, are found worldwide. They are small shrimplike crustaceans with a heavy carapace covering their thorax. They are commonly called opossum shrimp because the females carrying their developing young in a bulging pouch or marsupium formed by thoracic plates at the base of their legs (Giwojna, Oct. 1996). The average life span is about 12 months and adult mysids seldom exceed 1 inch in length. At least 460 Mysis species are found around the world (Bentley, 2002), and wherever opossum shrimp occur, they form a large part of the indigenous seahorses’ natural diet. They are snapped up greedily by even the most finicky syngnathids, including the fabulous but delicate Seadragons (Phycodorus and Phyllopteryx sp.). In fact, large seahorses are so fond of these crustaceans that they scarf up frozen Mysids with relish. This is superb food that should form the basis of your seahorses’ diet if you can possibly obtain it–live, fresh, or frozen (Giwojna, Oct. 1996).

So that’s one method of going about it, Erik. If you search the Net, you’ll find scads of information on culturing Mysis, which should give you a pretty good idea whether or not it’s practical in your case. For example, he sure to check out the following to online articles:

Best of luck wrapping up your skinny H. reidi with this superb food, Erik!

Happy Trails!
Pete Giwojna

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