Will my filtration / pumps kill the Copepods?

Will my filtration / pumps kill the Copepods?

A lot of hobbyists, especially those with a mandarin or other finicky fish, find themselves concerned that their pumps or filtration system will kill copepods, causing a smaller population. Is this something you should be worried about, or is it something that doesn't deserve a second thought? You may get tired of hearing this in the aquarium hobby, but it depends. Before we determine if this question matters at all, let's determine if pumps or filtration is a threat to copepods. Then, we'll discuss how you can maximize the amount of copepods in your aquarium.

Copepods are small

There are lots of copepod species (we're talking thousands). There are even some copepods that are parasitic. However, let's agree that we are specifically talking about copepods that are commonly found in the marine aquarium hobby, such as the copepods sold by AlgaeBarn.
Those copepods can grow to a max size of around 1000 micrometers, which is 1 mm or 0.039 of an inch. That is incredibly small. That means that full-grown copepods are just barely observable with the human eye. Even then, they only appear as tiny little specks. But, that's only considering full-grown copepods. The majority of copepods are smaller than that. A copepod nauplii can be as small as 100 micrometers ( 0.1 mm or 0.0039 of an inch). The moral of the story is that copepods are very, very small.
A lot of copepods are so small that getting chopped up by a pump would almost be a miracle. Pumps are not a threat to copepods. Copepods can handle lots of flow; we're talking levels of flow that are found in the ocean. If they can handle that, your aquarium pumps are certainly nothing to worry about.
However, your filtration can be a different story. A copepod has a much smaller chance to make it through a skimmer and some mechanical filtration. It's not that the skimmer or filtration would kill the copepod, it's more that the copepod would not be able to get through the way it can get through a pump. The only filtration equipment that may actually kill some copepod is a UV sterilizer. Even then, it's unlikely it would kill a substantial amount of copepods.
Will your filtration or pump kill copepods?
No. However, filtration can make it more difficult for copepods to find their way into your display tank.

Get the most out of your pods!

How can you maximize the amount of copepods in your aquarium? Well, first you need some sort of refugium. Refugiums, as you may or may not know, offer a place for copepods to reproduce and live without being eaten by aquarium fish. Over time, copepods will make their way into the main display. Even if you only added copepods to your refugium, your display would end up being filled with them eventually, though that depends on the fish in the tank. The point is that copepods will make their way from your refugium to your display no matter what. However, there are a few decisions you can make early on to increase the frequency of this happening.
The most important thing to consider is the layout of your sump or filtration system, more specifically the order. Now, you probably see why this is more of something to determine at the beginning. In regards to a sump, it is not uncommon to see the refugium come before the protein skimmer and media reactor. If you are not concerned about maintaining a stable population of copepods in the display, this may not matter to you (although there are some other reasons this layout can be less functional). If you are trying to maximize the amount of copepods that make it form the fuge to the display, it is best that the refugium is the last thing before the return pump. On a side note, the other reason you may want to have the refugium before the skimmer is so that organic waste can be removed by the skimmer instead of getting stuck in the refugium. It allows both the skimmer and the refugium to work better. If you can, avoid using any sort of mechanical filtration after the refugium as well. If for some reason, you just can't put the refugium last, it's okay. Copepods will still find their way from the refugium to the display. It just won't be as much.
Another factor that comes into play is how you add the copepods into your aquarium. Again, this is obviously not something you have control over after you add them, but it is important. The best time to add copepods is when the aquarium lights turn off at night. Once the lights are off, turn off all of the pumps. That includes the skimmer and power heads. Next, remove your filter sock if you have one. Add about 30-50% of the pods to your refugium and add the rest to the display tank. If you want, you can use a turkey baster to spray the pods directly onto the rocks. Leave the pumps off for 30 minutes to a couple of hours. Keep the filter socks removed for 24 hours. This will ensure your aquarium is seeded with copepods the best it can be. If you added your copepods without using this method, chances are copepods will still multiply over time. However, if you want to ensure that your aquarium is properly seeded, buy more copepods and do it the correct way.

 Finally, you need to make sure that your copepods have a habitat to live in. While they will live on just about any surface in your aquarium, providing them an ideal habitat will allow for more reproduction and more copepods. Macroalgae makes an excellent habitat for pods. How convenient is that? You probably already of macroalgae in your refugium! If you don't, you should certainly get some. Macroalgae is a great habitat for copepods but it also helps with nutrient export. The copepods will also help keep your macroalgae clean of detritus, allowing it to grow more. Along with macroalgae, you can also use MarinePure ceramic media in your refugium. Not only does this provide a great place for copepods to live, but it is also perfect for beneficial bacteria.
With all of that, copepods should be thriving in your aquarium!

Worth the effort?

Why care about any of this? Is all of this worth the effort? Is it worth it to rearrange your sump for tiny white dots? Again, it depends. If you have an aquarium without any copepod demanding fish, all this effort may not be worth it. Should you still add copepods? Most certainly. Copepods have many more benefits than just feeding. They can feed corals, cleanup detritus and algae, and bring more biodiversity and stability.  However, it may not be worth rearranging your sump, unless you are doing it to make your skimmer and refugium work more efficiently. It will not be the end of your tank or its inhabitants if you have your refugium first, though more copepods can certainly benefit your tank. When it comes to those with or wanting a Mandarin Dragonet or some other finicky fish, making your copepod population stable is a must. A Mandarin Dragonet can eat thousands of copepods in one day. Without a refugium properly providing copepods, a Mandarin can quickly wipe out a tank's copepods population. That is why a refugium is so important, and if you can make it work better, it is certainly worth it.
Take this information as advice, not gospel. Do what is best for your system. While having a refugium last is usually best, there are certainly situations where it might not be possible. Although you should add copepods at night, you can indeed add them during the day to simply feed your fish. It all just depends on what you want to do with your aquarium. When it comes down to it, copepods are extremely resilient organisms. No pump or protein skimmer can stop them from spreading around. Whether you need them to spread around more is up to you to decide. 
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