That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here. There was a time when all serious aquarists maintained live cultures of Daphnia. This practice has fallen out of favor today, with live foods being replaced by prepared diets. However, many tiny aquatic Crustaceans are easy (and interesting!) to maintain, and represent one of the most nutritious of all food sources for aquatic animals.

The animals highlighted here are especially valuable for fry and small or filter-feeding invertebrates, and are essential to the survival of tiny live food specialists such as seahorses and pipefishes. They can be used for freshwater or marine animals. Be aware, however, that freshwater species will expire rapidly in salt water, and vice-versa.

Daphnia

These tiny Crustaceans may easily be collected via plankton net (available at biological supply houses) from nearly any body of fresh water. Alternatively, a culture may set up by adding pond water and grass or hay to a tank placed in a sunny location (or use a full spectrum bulb).

Eggs or immature Daphnia magna, a very common species, will likely be present and, at 75-80 F, will mature within a week. This species reaches 0.25 inches in length (a Daphnia giant!) and is sometimes available commercially. Females produce 100 or more eggs every few days (with or without males), and so a healthy colony will easily meet the needs of most aquarists.

Daphnia fare best in tanks supporting a healthy growth of algae. While filtration is not essential, I’ve found a sponge filter
to be very beneficial (use a small air pump – strong currents should be avoided).

Decaying plant matter provides sufficient food, but growth and reproduction will be hastened if you supplement the culture with Artemia food , ground Spirulina discs and liquid invertebrate foods.

Copepods

Smaller even than most Daphnia, Copepods are an excellent food source for the tiniest of fish fry, shrimps and filter-feeding invertebrates. I’ve used them for dwarf seahorses and newborn four-spine sticklebacks with great results.

Occurring in fresh and marine waters worldwide, over 5,000 species of these crustaceans have been described to date (Copepod taxonomists must be quite amazing people!). Cyclops fuscus, which reaches 0.124 inches in length, is the species most commonly encountered in the USA.

Copepods may be collected and raised as described for Daphnia.

Seed Shrimp or Ostracods

These aptly-named Crustaceans (Class Ostracoda) do indeed resemble tiny shrimps encased within a seed. The 13,000+ described species thrive in a nearly every aquatic habitat known, from the deepest oceans to the few drops of rainwater that collects in bromeliads growing in rainforest canopies. They are truly amazing in their range of forms and adaptations.

Seed shrimps “bounce” along the substrate, a habit that renders them an ideal food for bottom-dwelling aquarium pets. Although rarely cultured for food, I have found them to be quite hardy, and well worth the small effort involved in keeping them. Their exoskeleton is an excellent source of calcium.

Seed shrimp care is as described for Daphnia.

Useful Products

A number of highly nutritious crustacean-based foods are available to supplement live-food diets. The following are well-worth trying:

• Zooplankton Diet
• Liquid Invertebrate Foods
• Freeze-dried/Frozen Daphnia

Further Reading

Despite their small size, seed shrimps are incredibly complicated creatures, and quite interesting in their own right. Read more about their structure and behavior at http://w3.gre.ac.uk/schools/nri/earth/ostracod/introduction.htm.

Please write in with your questions and comments. Thanks, until next time, Frank Indiviglio.

Copepod image referenced from Wikipedia and originally posted by Uwe Kils

Please welcome back Desiree Leonard to That Fish Blog.

We as biologists at times take our knowledge for granted and forget that not everyone that is involved in the hobby is fully aware of all of the natural processes and progressions which occur in a saltwater aquarium.
Frequently we are contacted by frantic new aquarists with the following:  “I have little bug – like things crawling all over the rock in my saltwater tank.  I swear they weren’t there before.  What are they and where did they come from? Are they going to make my fish sick?  How do I get rid of them?”

Well, after talking the caller down off the ledge (so to speak), I give this answer:

In all likelihood, these are Amphipods and Copepods; shrimp-like crustaceans that dwell in the substrate and rocks.  Because of the thousands of species contained within these groups in Class Crustacea, I am not going into detail about the taxonomy of these organisms, but here are some basic facts about these tiny crustaceans.
• There are both pelagic (free swimming), and benthic (bottom dwelling) bugs.
• Copepods occur in all types of aquatic ecosystems; freshwater, estuarine (brackish) and marine.
• Amphipods are mostly found in marine ecosystems, but there are some freshwater and terrestrial species.
• They are just a few of the tiny animal organisms that make up zooplankton, which contributes to the overall make up of plankton.
• These creatures eat phytoplankton (tiny plants and algae that also help make up plankton), small microzooplankton (the division of zooplankton that are smaller than 200 microns, or 1/127th of an inch in size), and detritus.
• Only a few of the thousands of species of copepods and amphipods known are carnivorous or parasitic, and these are rarely found in a saltwater aquarium system.
• For many saltwater fish and other marine species, copepods and amphipods are a primary food source, both in nature and in captivity.
• Because these tiny organisms are a natural part of the plankton food chain in the ocean realm, they are naturally going to occur in a saltwater aquarium environment. They are also micro-cultured as food for various species of adult marine animals, as well as used and tested as a food source in the research of culturing and rearing all kinds of tank-raised fry.
• Copepods and amphipods most often appear in closed aquarium systems after live sand and/or rock has been added.  They will “bloom” in the tank when the temperature is slightly warmer and a food source is available.

Another critter that may be seen is the isopod.  Also called pill bugs, fish lice and rolly-pollies, these animals are found in all parts of the marine environment.  Most isopods are free living and harmless, feeding on detritus and algaes, however, some are predatory, or parasitic, and dangerous to other reef aquarium animals.

How did these “pods” get into the tank?  Well, they’ve most likely been there for a while, just not in numbers large enough to notice.  These organisms are microscopic or plankton sized when they start out, so until they grow large enough to be seen with the naked eye, you don’t know they are there.   They hitchhike in on live rock and sand, and it is only after you have placed it into your aquarium that these organisms crawl out and make themselves at home.

If you have a large population of “pods” naturally, count yourself among the lucky few.  Many aquarists go to great lengths to create a large healthy population in either their tank or refugium.  Remember, these “bugs” are a natural part of a healthy aquarium ecosystem, as well as an important food source required by some species to survive.  In most cases they won’t hurt anything.  You shouldn’t have to do anything about them.  If you are concerned however, you can provide a natural predator which should keep the population under control.  Here is a list of species which pick at live rock, or sift substrate in search of these tasty morsels.  Keep in mind those fish marked with a * are species which feed on these bugs as their primary food source.  They are challenging to keep, requiring a well established aquarium with a consistently high “pod” population to live on lest they starve.  Keeping more than one of these obligate “pod” eaters in a tank will most likely lead to a depleted food source.
• *Mandarinfishes/Dragonets; Synchiropus splendidus Blue/Psychadelic Mandarin, Synchiropus picturatus Green/Spotted Mandarin, Synchiropus stellatus Red Scooter/Starry Dragonet
• *Sand sifting gobies; Valenciennea spp. Sleeper Gobies, Signigobius biocellatus Twinspot/Signal Goby
• Most Firefishes are planktivores which may occasionally pick these bugs from the rock.
• Most Angel, Butterfly, Hawk, and Wrasse species spend their days grazing on fauna found on the rocks, however, do not consider this as a primary food source – merely an opportunistic treat.
• Seahorses feed primarily on these “pods” but are not a beginner fish and should not be housed with other fish.
Amphipods, copepods, and isopods are just a few of the fun little hitch-hikers we get questioned about, and we enjoy helping our customers with identification issues.  If you should have other fun things pop up in your ecosystem, here are some other things you can do to help identify them:
• Buy some good invertebrate identification books for your saltwater reference library.
• Refer to marine invertebrate database and profile information, as well as photo galleries.
• If you have a personal saltwater Web site, create something like a “Can You Help Identify This?” page. You can display photos here and allow visitors to email back to you about them.
• Post a message in various aquarist forums asking for help with identification. If possible include a photo of good clarity, or provide a link to a Web page you may have created as described above.

*Photo Emailing Tip: When you email a photo to another aquarist asking for help with identification on something, be kind. Only send an image that is reasonably sized, and is clear enough to tell what you want identified including a “brief” description.

Thanks,

Until Next Blog,

Desiree