Canister Filters for Reef Tanks? Are They Good or Not?

Updated on January 15, 2021 by

Canister filters have been the best filtration option in a long while for larger tanks in the freshwater world, but are they suitable for saltwater tanks too? Let’s find that out.

We’ll be looking today at canister filters and their marine aquarium applications, whether FOWLR (fish only with live rock) or mixed reefs.

If you’re interested in getting a new canister filter suitable for most aquarium setups, you may take a look at our article on the best aquarium canister filters.

But let’s first examine some basics of how do canister filters work.

They incorporate several baskets for different filter media types and a small circulation pump housed inside a compact case, wholly sealed so no water can get in. Once an initial siphon is performed, the pump draws water from the tank through the inlet tube. It then passes through several mechanical, chemical, and biological filtration stages. Once the water reaches the canister’s end, it gets back into the pump and is returned to the tank via the outlet tube.

One of the most significant issues that canister filters come with is that they can be tough to clean out, which is valid with most aquariums equipment. Canister filters will collect waste and residues in time, meaning that it will need to be periodically cleaned.

For reef tanks, the importance of protein skimmers can’t be emphasized enough! For that, you can take a look at our corresponding article that shows a comprehensive list, carefully selected best protein skimmers.

Unfortunately, when they are unplugged for maintenance sessions, canisters are entirely filled with water and don’t have a great way of draining it, depending on the model you have. Most filters have a way to lock the inlet and outlet to maintain the drain siphon while still allowing you to move the filter away from the tank first.

But first of all, anyway, you’ll need to disconnect the filter, so the filtration pump gets shutdown. The next step is just to unlock and remove the inlet and outlet tubes and take the canister to a sink outside or wherever you choose to do your aquarium maintenance from here. Next, drain the filter and remove the media while double-checking your mechanical and chemical filtration and replace it if that’s needed.

Also, take a look to see if your biological media has started to collect any waste. If it’s become too dirty, take either the water you’ve just drained from the filter or some mixed saltwater you just prepared so the media can be rinsed in it.

Consequently, you just have to make sure that you clean the biological media in saltwater; otherwise, you’ll kill the bacteria that colonize it.

Once everything is clean again, you can place the media back in and hook the canister filter up to your tank. Before starting the filter, it’s also a good idea to prepare some newly mixed up saltwater that you’ll need to replace whatever you’ve drained from the filter in the beginning. Therefore, why do canister filters have a terrible reputation when it comes to saltwater tanks?

Well, in a fish-only marine environment, you can absolutely put a canister filter to use next to a protein skimmer. But this isn’t always the case for reef tanks. Once you add corals to a tank, everything gets a little bit more complicated. Unfortunately, canister filters just don’t scale up to the filtration expectations in such reef environments.

Fortunately, as an alternative to canister filters for marine setups, we have the sumps. Sumps hold much more water than a canister filter, significantly adding to your total setup volume and keeping your marine parameters stable and optimal as well.

Secondly, due to their lack of size, there’s simply not enough surface area in canister filters to facilitate bacteria growth when compared to a sump. This, however, can be compensated by filling your canister mainly with biological media.

But even then, there may not be enough space to make up the difference as fish are a little less picky than corals.

Therefore, a canister filter is likely a better fit for fish only with live rock tanks.

Remember that you’ll still need to perform regular maintenance on your saltwater canister filter and replace your media on a schedule. Otherwise, you’ll risk letting the filter become a nitrate factory. Despite these disadvantages, canister filters can still definitely be used on marine aquariums but are often best installed with nano tanks where a sump just isn’t practical due to its size.

Fluval and Eheim, for instance, are great manufacturers of canister filters that are suitable for both saltwater and freshwater environments.

Among the best canister filters for aquarium that we recommend in our related article, are similar in many aspects, but each one has some different key features that may appeal to you more. Thank you for visiting us today!