External Aquarium Filters

Sometimes the question “can I use my freshwater canister filter for a marine aquarium” pops up and the answer to that question is yes as long as you clean the filter first.

Mechanically most external filters don’t mind working in an salt or fresh water environment. The mechanics just don’t change. Your filters pump is powering the water flow through your filter no matter if it’s salt or fresh water.

The differences start at the filter media you’re using. As an example in a fresh we use Zeolite filters to absorb ammonium from the water, but this trick doesn’t work with salt water. The same hold true for some "scavenger resins" used in some canisters.

Thus you can use the same external filter but will sometimes need different filter media. The mechanical and sponge filtration remains the same. Most biological filtration remains the same and most media are developed for use in both environments anyway. Follow the instructions of the manufacturer.

There is one thing to keep in mind though; a marine aquarium is often more susceptible to small disturbances in balance then a fresh water tank. This makes maintenance of the filter and it’s media to a top priority.

In a marine aquarium you will often use a protein skimmer; this won’t work in a fresh water aquarium.

So canister filters can are usually suitable for fresh as well as salt water but there are some differences in the filter media used. A protein skimmer is great for marine, but it won’t work in your fresh water tank. More often than not you will want a higher flow-rate of water in a marine aquarium.