I recently had someone ask me about using a refugium versus a sump filter on his 60 gallon aquarium. He is currently running a canister filter and considering his options. I’ll talk about the pros and cons of each filter, and what that means for the system.
Canister filters range from many sizes and styles. In general, they are great filters. The way these filters work, is basically like a siphon. Even if your filter isn’t plugged in, you can prime it by starting a siphon (since a canister filter is mostly tubing), and with no power, water will be forced through the canister media. It will also be forced up the return tube going back into the tank, but only up to the level of the water in the tank (It’s important to note that this works best if the outflow is out of the water, reducing pressure on the moving water). So the filter only needs to push a little to get the water moving back into the tank. So they do generally work very efficiently, and they can hold a ton of media to aid in filtration, assuming of course, your filter allows you to do that. Eheim classics are great because it is basically just a canister. Of course, Eheim sells specific media for that filter, but let’s say you needed to run more carbon, or more filter floss, or a few different things. That simple type of canister allows you to customize it quite a bit. Other filters may have very specific media inserts that allow for less customization.
So, we’ve established that canisters can be great filters, but one of the things that people like best about them is their ability to go for longer periods than other filters without being serviced. With respect to a reef tank, this is not an ideal situation. For starters, we don’t want to go long periods without maintaining our reef tanks, especially running our water daily through a canister full of waste that we cannot see into. The other thing is that most people run bio-media in there to grow their beneficial bacteria. We want to grow these bacteria in our tank, on our live rock and live sand. Often times people refer to bio-balls and other filter bio-media as nitrate factories, since they can convert toxic fish waste to safer nitrate very quickly and efficiently. I prefer to develop the tank in a more natural way, forcing the live sand and rock to grow the bacteria that process waste (That’s why we use them in the first place!), and this allows the tank to begin to take care of itself. When you set it up right, the tank will even consume the nitrate (Via deep sand bed or growing macro algae), keeping your water cleaner and probably reducing algae growth.
A refugium is, very simply put, a place of refuge, and they can have many different functions. This could be a place to grow natural foods like copepods that might otherwise get eaten in the main tank. It could also be a place to grow and protect algae to uptake nutrients (as algae grows, it eats waste out of the water). People often put live sand or some sort of refugium mud to also aid in taking up nutrients and growing certain algae. There is even a type of refugium called a cryptic zone, which gets no light and is used to grow live sponges which are fantastic natural filters.
But refugiums come in many different forms. There are store bought hang-on-back refugiums, people may dedicate a chamber in their sump to build a fuge, or even use just another tank. Because refugiums aren’t a requirement, people will usually have a reason they want to setup a fuge. Want a finicky fish? Grow copepods to help with its diet. Have an excess of nutrients? Grow algae and age a deep sand bed. Want corals but have coral eating fish? Grow corals! You can do all sorts of things in a fuge, if you choose to start one.
Sumps can be great for plenty of reasons. For starters, it gives us a place to hide things like heaters, protein skimmers, and it also gives us more gallons in our system, making it more stable. Depending on the size of the sump, you can also do other things like add additional filtration like bio-media (if necessary), a filter sock, or a UV sterilizer. Some people grow frags or separate problem fish down there, run a media reactor, or even build a refugium. Commercially produced sumps are usually acrylic, and often kind of expensive. They come in various configurations, like reef-ready or the traditional bio-ball setup. However, many people skip this step and save money by using an old tank for their sump.
Thoughts – I have never run a fuge on my own tanks since I have never really needed one, but I have helped many people set them up, and I’ve worked with plenty of them. In my opinion, I like building tanks that can sustain themselves, and they never include a refugium. They are great additions on any tank, but proper planning elsewhere can save you the trouble of buying the stuff for a fuge, as well as figuring out how to incorporate one into your system.
So what I would recommend to someone asking the original question would be to run a sump. I would suggest finding an appropriate sized tank to re-use as a sump to save money. Since there are many different sizes of tanks, you should find one long enough to hold all your stuff, and short enough to be easy to work in, without being a flood hazard. Acrylic tanks are nice because they can be drilled more easily than glass (if you even need to drill it for some reason), but often times they have a top brace that makes the opening on top much smaller than the footprint of the tank. This can be real tough to work in, and that difficulty gets very old very fast. But glass tanks are always open on top, easier to find, less expensive, and come in more standard sizes. They sell filter sock holders to easily add mechanical filtration to any glass tank sump. You can also use silicone to install glass or acrylic sheets in the sump to create different chambers. These chambers might be used to hold bio-media, create a place for coral frags, or even set up a full blown refugium within the sump. Maybe all of the above!
Feel free to post follow up questions and see them answered on the site.