Copepods and Amphipods are microscopic crustaceans that form an essential link in the marine food chain. These tiny organisms are a natural part of the plankton food chain in the ocean(there are Freshwater copepods, too). They graze on phytoplankton, bacteria, and in some cases, detritus. They incorporate the protein and fatty acids from these food sources and concentrate it into a highly nutritious package for consumption by marine animals.
These little critters are mari-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.
Marine Animals That Eat Amphipods/Copepods
Amphipods are an important food source required by some fish species to survive in the wild. Many of these fish will starve to death in an aquarium if and until they can be weaned off to other, more convenient hand fed foods such as frozen Mysis Shrimp, Brine Shrimp or other finely chopped meaty fare, such as Krill. Some fish, such as the Mandarin/Dragonette and Sea Horses are found by most aquarists to be extremely difficult to get to eat anything other than amphipods/copepods.
Many marine fish, especially in the larval stage, cannot survive without the "essential" fatty acids found in amphipods and copepods.
Where to Culture
Copepods/Amphipods can be cultured in almost any suitable container. Some people use a 5 gallon plastic bucket, others use 10 gallon aquariums. All you really need is a container that you can keep you growing medium (old bio balls, live rock, old filter pads, coarse sand or crushed coral) wet, supply with an air supply (airstone) and sufficient light. DIY Glass Aquariums are an excellent way to create the exact tank you need for a minimal price.
There are a lot of theories about filtering a 'pod grow tank. The natural biological filtration offered up by live rock, or a sand bed that contains nitrifying bacteria, and/or microalgae (not Ulva, which has little surface area for the mass Chaetomorpha, Caulerpa, and Halimeda are excellent!) are probably best. The downside to Halimeda is that it is calciferous and will require calcium additions.
A simple airstone with a medium air flow should be enough to keep the water moving in the culture vessel.
You will probably want to avoid using a protein skimmer, as it will have a tendency to capture the free-floating copepods/amphipods.
Culture Surface Area
Amphipods are both pelagic (free swimming), and benthic (bottom dwelling) bugs, but are primarily bottom dwellers and thus spend most of their time on the bottom surfaces in an aquarium. It has been our experience that amphipods have more of a tendency to rise from the bottom of the aquarium and enter the water column at night. If there are large quantities of amphipods in a tank, they can easily be seen with a flashlight a few hours after dark.
Amphipods do best in an aquarium containing large surface areas to graze on, such as old bio balls, live rock, old filter pads, coarse sand or crushed coral substrates. From personal experience, Amphipods/Copepods grow very well in an inexpensive UGF with a coarse crushed coral substrate.
Amphipods/Copepods don't really need a lot of light in order to grow or reproduce. Most people have found that 12 to 16 hours per day of minimal (ambient daylight, small wattage incandescent or LEDs (the little clamp on LEDs are perfect)) work well. If you are using macroalgae for a growth medium, you will want to supply the right amount of light for their health.
Maintain the salinity of your Copepod/Amphipod system at the level of the target tank you will be depositing them into. If you are using an in-line refugium with your main tank, you won't have to worry about it.
Maintain a stable temperature between 72-82 degrees is best. Amphipods/copepods are cold blooded, so the warmer the water, the more active (feeding and reproducing) they are, to a point. Don't "cook" them. Temps above about 85 could be harmful.
Amphipods aren't necessarily predatory but they do prefer meaty foods. They are omnivorous but tilt toward the role of carnivore much more than herbivore. Feed meaty foods that break down fairly quickly in the water column. A good mixture of marine marine pellet and marine flake foods, ground up in a mortar and pestle will yield terrific results.
You can also culture phytoplankton in a 2 liter plastic bottle to feed your copepods. There are a number of complete phytoplankton culturing kits available online.
Don't overfeed! The bugs will consume what they can consume and no more. Putting more food in the tank will not make them eat more. Test the ammonia in the tank to see if you are feeding too much. If your ammonia readings start to spike, perform a water change to lower the level and cut back on the food. It may take a bit of experimenting, but you should be able to find the right amount to periodically introduce to the tank.
If an inline refugium is being used, little maintenance will be needed. A stand-alone system will need a few water changes (once per month or replacing water after harvest) will suffice, as long as feeding is not over done. Gammarideus are amazingly tolerant and tend to thrive in higher nutrient systems (more food).
Harvesting can usually be done by siphoning the critters into a fine mesh fish net. If you are using old filter pads for a growth medium, just remove them from the growth tank and take them out in a bucket of tank water, then pour the water through a net. If you are using a crushed coral substrate, siphon the substrate the same as you would your tank bottom, using a fine mesh to catch the Copepods/Amphipods.
Introduction Into Aquarium
Copepods and amphipods most often introduced into closed aquarium systems when live sand and or live rock has been added. They will begin to multiply and grow in the tank when the aquarium water temperature is slightly warmer and a food source is available.
Perhaps the least expensive source of copepods and amphipods is friends who have saltwater aquariums with a good population. If you can get them to harvest some of their excess and donate them to you, you will have a good start on your pod population.
Live copepods are also available online (on line example is AlgaGen ReefPods (Compare Prices)), in a bottled form.
Once you have your Amphipod/Copepod culturing system set up and running and worked the wrinkles out of feeding, maintenance and harvesting, you will find that the system is an easy, low cost method to provide a high nutrition food to your difficult to feed tank critters.