As hardy and inexpensive as Goldfish are it may seem like a bit of an extravagance to pick up something as complex and even pricey as a filter! After all, we’ve all seen Goldfish bowls before! Do Goldfish really need a filter?
Do Goldfish Need a Filter?
Goldfish should absolutely have a filter, no ifs ands or buts. Filtration is essential to any enclosed aquatic space that isn’t designed with some sort of biological replacement in mind (Walstad planted aquariums and refugiums are notable examples).
Fish, like all living creatures, take in nutrients and release waste. All of that poop and ammonia has to go somewhere – and the sooner, the better. We’ve all probably had a goldfish bowl before so many people think that they can thrive in small stagnant pools of water.
But is your Goldfish still alive today? Because they can live 30-50 years if well cared for in spacious aquariums or ponds. If not then the lack of filter almost certainly contributed to its early demise.
Nitrogenous waste (ammonia, nitrite, nitrate) builds up and the beneficial bacteria that normally break it down don’t find the cozy home that a proper filter provides.
Many live in the water column and even in the substrate. But filters provide loads of extra surface area for these micro organisms to colonize thanks to the cotton filter floss, internal foam pads, and ceramic blocks.
What Type of Filter is Right for Goldfish?
Whether you have a bowl, aquarium, or container pond, one of these filters is just right for your Goldfish needs!
Sponge filters are a little less popular than they were a few decades ago now that power and even canister filters are significantly less expensive. However they absolutely still have a place, especially in space and cost-limited environments like fish bowls!
Sponge filters work by using airflow to channel water through them. Water is strained by a large foam block that initially only provides mechanical (physical) filtration, like a mesh screen.
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As floating bits of food and feces get caught in the foam, beneficial bacteria take up residence in the foam. These then break down free ammonia into nitrite and nitrate over time. Even the simplest sponge filter can add thousands of square centimeters of surface area for biological activity to take place on!
While sponge filters don’t usually provide any chemical filtration they are excellent options for bowls or smaller aquariums with few fish. Just make sure you keep up with your water changes to remove nitrate, which isn’t broken down by sponge filters.
The majority of aquarists with goldfish tanks are using power filters. Power filters use a magnetic impeller to suck water in actively from the aquarium into a series of chambers.
Each chamber has a medium designed to provide mechanical, biological, and chemical filtration before returning water to your tank. These units typically sit on the side or back (hang on the back) of your aquarium. But some styles are even submersible!
Chemical filtration is great because it can target specific elements that the other two types miss or don’t act on quickly. 95% of power filters include activated carbon (charcoal) granules for chemical filtration.
Activated carbon works by adhering to free floating organic proteins, amino acids, and other compounds that are normally bacteria food. They get locked away in the activated carbon where filtration bacteria can immediately digest any released ammonia or nitrates.
Power filters often have a strong enough outflow that they even provide some extra aeration via surface agitation! In short, they are some of the best filters for Goldfish!
Canister filters are the no-holds barred option for Goldfish tanks. If you have a high fish load and need extra space for custom media then a good canister filter can keep even heavily stocked tanks pristine.
Canister filters typically sit under the aquarium and have pumps that create a very strong outflow current. Typically they are used for aquariums 55 gallons or larger but there are several mini canister filters nowadays for smaller tanks.
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They also provide the highest degree of customization as most of the space is dedicated to spacious media baskets. Some models require brand-specific cartridges.
But I prefer designs that let me choose whether I need activated carbon, zeolite resin, ceramic rings, or some other media that I know will target a specific issue!
What If I Don’t Want a Filter?
There’s little reason not to own one as they are inexpensive, reliable, and highly efficient at processing fish waste. However there are a few alternatives to filters that can work well assuming you keep up with them!
Fast growing aquatic plants like Water Wisteria (Hygrophila difformis) and Anacharis (Elodea densa) can pick up a lot of slack in the water quality department! Since they put on biomass quickly they help lock away ammonia, nitrite, and nitrates so they won’t come back to hurt your fish.
Best of all, most plants preferentially take up ammonia, which is the most toxic waste product Goldfish create. Therefore they consume it as soon as it reaches them.
The main drawback to keeping live plants with Goldfish is that they find plants delicious! Fast growing plants also tend to be soft, heightening their appeal to your fish. Goldfish also root along the bottom constantly, disturbing and uprooting plants with their digging.
If you’re going to rely on plants to provide major filtration then you need to keep a very low bioload. Plants also tend to work better in outdoor ponds, where they can get plenty of sunlight and aren’t as likely to be disturbed by a passing Goldfish. Even if the Goldfish graze them on occasion the plants will outgrow any browsing!
Frequent Water Changes
Water changes are the easiest and most efficient way to go filter-less with a Goldfish aquarium or bowl. How much and how often depends on the aquarium size and how many Goldfish you’re keeping.
I’d recommend keeping a moderate fish load if you’re going down this path because it won’t take much to send the aquarium into a spiral of disease. A single dead fish or overfeeding can cause serious ammonia issues if you don’t have a filter to take up that extra waste.
While they are common and very affordable, I only recommend keeping chemical waste neutralizers as a last resort. Having an ammonia absorbing resin or liquid agent is great. But the residual chemical byproducts are typically less toxic than the original, not simply harmless.
We don’t want any of these chemicals building up in our aquarium either. These are used to buy aquarists time until you can do a proper water change on your tank!
Much like Bettas, Goldfish can survive not having a filter. But it’s not at all healthy for your fish. We don’t want our pets simply surviving, we want them to thrive in our care! So make sure your Goldfish has adequate filtration and he will reward you with decades of life!