Serious question. What do copepods eat? There are many misconceptions about what those loveable little plankton like to snack on. You may have your fish’s nutrition dialed in. The specific gravity of your tank might be exactly perfect to three decimal places. Heck, you might even have an entirely self-sustaining copepod culture in your reef, but there’s a chance you might not be feeding them exactly what they crave.
To understand what they like to eat, we first have to understand how they eat. Copepods, you see, are small, planktonic crustaceans who basically only drift around the water and eat. Depending on the type of copepod you culture, yours may tend to either latch onto live rock, or just drift around unattached.
They can, in fact, swim using a smooth swimming movement or a quick, pouncing movement. The former is used for getting places, while the latter is utilized when prey is near. Still, they prefer to not so much hunt as graze.
Their vagabond-y nature makes their optimal food other small, drifting particles. Depending on the type of copepod you decide to raise, they might need either a herbivorous diet or an omnivorous one.
Since copepods are “opportunistic feeders”, they eat most things that drift their way. Instead of actively searching for food like, say, a Mandarin Goby, they prefer to let food come to them. Copepods are incredibly small, so they prefer to gnosh on small, particle-like food.
When a tasty-looking bit of food comes their way, a pair of special feeding appendages, a bit like antennae, start to swish the water towards their mouth. Like an amoeba, copepods engulf their food with a specially designed mouth.
Obviously, the type of food they can eat has to be incredibly small, but by no means are their food sources limited. Copepods are a little like the garbage disposal of the ocean; anything they can eat, they will eat.
For that reason, many reefers feel content to just let their copepods eat only the detritus floating around in the water. While they do eat algae particles, feces, and other nasty junk organically produced by your reef creatures, that’s not the only thing they should eat.
Just like any other animal, your copepods are just as nutritious as the food they eat. While they might survive on a strict diet of detritus, they’ll be a whole lot like junk food- low in nutritional value.
On the other hand, if you give you copepod a steady dose of delicious phytoplankton (Green Phyto works great!), they’ll take on the nutritional value of the phytoplankton, which just so happens to be super nutrient-dense and full of vital compounds.
Watch out for the type of phytoplankton you get. Be a discerning consumer- now is not the time to go cheap. It’s true that there are many types of dried phytoplankton on the market, but they are simply not as good. When they’re dried, their chemical structure and the way they’re metabolized changes.
Imagine them a bit like a salad. Which food do you think will be more nutritious: A salad that has been dried and left to sit for a while before being eaten weeks later, or a fresh picked salad straight from the garden.
Phytoplankton are the same way. Live phytoplankton retain much more of their healthful compounds and nutritional values. After all, it is how they’re eaten in the wild.
Just remember the golden rule when incorporating phytoplankton into your copepod’s habitat; a light “green tea” color is the optimal concentration.
Additionally, depending on the type of copepod you’re raising, you could do well to introduce some high quality Rotifers into the mix. Breeds like Tigriopus californicus, or Tiger Pods, thrive on the addition of well-fed Rotifers.
In fact, Tiger Pods and other large copepods grow much faster on a diet that includes Rotifers, thanks to the rich stores of fat and protein they contain. Luckily, Rotifers will eat the same phytoplankton as the copepods, so no sweat there.
Again, it’s important to feed the copepods a mixed diet of both detritus and phytoplankton, not one or the other, if you want them to truly thrive. The gold-standard of a copepods diet is something that resembles their natural, wild diet, not some laboratory supplement packed with additives.