Copepods and amphipods are both "pods", but they are very different animals. Although copepods are arguably more popular, there are still those that seek out amphipods. Using microcrustaceans to feed your aquarium and keep your aquarium is great, essential even. These little "bugs" can feed your corals and fish while being a workhorse of your cleanup-crew.
Amphipods and copepods have been in the aquarium hobby for a long time. Copepods are one of the most common organisms in all bodies of water, so it makes sense to say they've been in the hobby since the beginning. They would find their way into aquariums via hitchhiking on rocks or corals. The difference now is that hobbyists can add specific species or mixes of copepods to their aquariums. But what about amphipods? Amphipods used to be a lot more popular, but are no longer sought after as much. What is the difference between the two, and is one better than the other? In this article, we'll go over exactly that!
To start, copepods are assigned to the subclass Copepoda, while amphipods come from the subclass Eumalacostraca within the order Amphipoda. From a taxonomy perspective, these two organisms are distinct. They are two separate invertebrates. The largest difference between the two is the size. Copepods might as well be invisible until they are mature adults, and even then they are just little white specs. Amphipods, on the other hand, can be easily seen with a naked and eye and even grabbed with fingers. Amphipods are small, but they are quite a bit larger than most copepods. Of course there are varying sizes within these two classes, but one is certainly larger than the other.
Differences in diet
Copepods eat a variety of different things, but they are mostly herbivores. Amphipods are mostly detritivores, which means they eat dead organic material such as uneaten fish food and fish waste. Both copepods and amphipods are great for keeping your aquarium clean. Copepods tend to help more on the algae front, while amphipods help with detritus. However, because amphipods are quite a bit larger than copepods, they will often eat any copepods they can find as well. Overall, copepods are probably more helpful because they will eat algae and detritus. They can also get into smaller places that nothing else can.
Which is best for feeding fish?
Amphipods are popular because they are so good for feeding fish. Fish of all sizes will go crazy for amphipods. The great thing about them is that you can harvest them from your refugium or algae scrubber and feed them directly to your fish. When it comes to feeding mandarins, copepods are probably better. Although copepods will eat amphipods, there are often amphipods that are too large for mandarins to eat. Amphipods are also less abundant. Because it takes more to feed a single amphipod than a single copepod, there will always be more copepods. That's just how basic food webs work. There will almost always be more smaller organisms than large ones. That being said, wouldn't a single amphipod feed a mandarin dragonet
better than a bunch of copepods? You would think so, but you have to remember that mandarins have evolved to specifically eat copepods, and amphipods are often quite a bit larger than copepods. It is not uncommon for amphipods to be too large for mandarins. Copepods are simply able to multiply faster and provide more food for mandarins. Also, they are potentially more nutritious because they consume nutrient rich algae. So, it's possible that copepods are the better nutritional option as well. Copepods are all around better at feeding dragonets. Amphipods, on the other hand, are better for feeding large fish such as wrasses.
Keeping amphipods and copepods together
As mentioned prior, amphipods will certainly eat copepods. They can actually eat so many copepods that they impact your copepod population. Generally, it is more important to maintain your copepod population than your amphipod population. So, is it possible to keep both without decreasing your copepod population? It is definitely doable. As long as you provide your copepods with places to hide without getting eaten, they should be able to maintain themselves. This is especially important if you want to feed a mandarin dragonet. When keeping or planning on keeping a mandarin, it might be best to try to avoid adding amphipods to your aquarium if you can. Check out this
article for more information on keeping copepods and amphipods together.
How amphipods get into aquariums
Copepods usually get added to aquariums by the hobbyists. However, amphipods are not sold as regularly as copepods. Most of the time, they get into the aquarium on live rock or coral frags. If you add live rock to your aquarium, especially if it is true live rock from the ocean, you will almost certainly get amphipods in your aquarium. If you want to avoid amphipods in your aquarium, avoid getting live rock and go the dry rock route instead. If you want amphipods, consider live rock. Just remember that live rock will potentially come with some nasty pests that are not fun to deal with.
So which one is better?
If you had to choose between copepods or amphipods, it's safe to say copepods are the better choice. For some hobbyists, it is best to strive for copepods only and no amphipods. For others, having both can be extremely beneficial. It will result in more biodiversity and encourage more stability. Of course, it comes down to your specific tank conditions and what you want from your aquarium.