Every aquarium is different, but for a majority of appropriately stocked aquariums, regular maintenance or cleaning, including a partial water change, should be done weekly or every two weeks. The more often you clean your aquarium, the less you have to do each time.
Cleaning an aquarium on a regular schedule includes several activities:
For example, if you perform a partial water change every week, only a 10 percent water change may be necessary. However, if the aquarium is left for multiple weeks between cleanings, a 40 or even 50 percent water change may be necessary.
This is assuming your aquarium is appropriately stocked, and not overloaded.
How Often You Clean Your Aquarium Depends on the Amount of Livestock.
There is no perfect answer that works for everyone when asked how often they should clean their aquarium. There is a relationship between the amount of livestock in the aquarium, the amount of organics they produce, and the efficiency and scale of the system’s filtration.
Balancing this relationship results in an aquarium that should be cleaned every seven to fourteen days. If you have overpowered filtration and there is very little livestock, you will have to clean the aquarium less often. You might go 14 to 30 days before the media becomes soiled and the water’s nutrient levels approach unsafe levels. If your aquarium is overstocked and the filtration is lacking, then regular maintenance may need to be done every few days.
The sections below will detail what signs to look for in your mechanical and chemical filtration, on your glass and décor, and in your water chemistry to know exactly how often you should be performing regular maintenance.
Armed with this knowledge, you can also determine the appropriate amount of livestock you can safely house in your aquarium.
How Often Should I Clean Aquarium Filtration?
Mechanical Aquarium Filtration
The filter media which removes large organic particles like fish food, waste, sloughed tissue, and other larger excretions is called the mechanical filtration. This media usually comes in the form of a foam or floss pad, cartridge, roller pad, or nylon or felt sock. Mechanical is the first stage of filtration.
The best way to tell when it is time to clean or replace your mechanical filtration is visually. By simply examining the media it's fairly easy to tell if it has become soiled. Even if the flow through the media is still strong and undiminished, the organic waste the media is storing is constantly being leached into the aquarium as water passes through and the organics further break down.
If the media appears dirty or soiled and the flow from your filter or sump has reduced significantly, it is definitely time to replace or at least clean or rinse the mechanical filtration.
Chemical Aquarium Filtration
The filter media in your reactors, the carbon in your filter cartridges and media bags, and other forms of media that specifically remove chemicals or elements from the water column are your chemical filtration. This media’s capacity to remove the desired chemicals diminishes as it adsorbs more and more of the chemical. Eventually, the pores, or in some cases, surface area of the media is “clogged” and will no longer function.
With most media of this type, like carbon, granular ferric oxide, or zeolite, it is difficult to tell visually if the media is spent or used up. Testing for the chemicals you're trying to remove will give you the best idea if the filter media is still removing those chemicals.
If your aquarium water is discolored, usually a yellow tint, and you add carbon to remove it, track the time it takes for the aquarium water to clear up then start to return to a yellow tint again. This will give you a rough visual estimate of when to replace your carbon. I should note, sometimes a yellow tint is tannins leaching from driftwood. Eventually, tannins will be completely leached out and no longer continue to discolor water.
If you're trying to remove nitrates, phosphates, or ammonia, test the water before you add the media, then once a week after to see if the chemical starts to trend back up again; that's when you should replace the media.
If you can’t easily test for the chemicals you're trying to remove, like heavy metals, most chemical media will have a manufacturer suggested frequency by which the media should be replaced.
How Often Should I Clean My Aquarium Glass, Décor, and Equipment?
Everyone has a threshold for cleanliness with their aquariums. Some of us allow a thin film of algae to grow over the glass before we take the magnet cleaner to it. Others wipe the inside of the glass every morning. In most cases, the amount of organic and chemical buildup on the glass, décor, and external equipment does not have a critical effect on the function of the aquarium; It's simply personal preference.
In some cases though, salt creep, calcium, and carbonate precipitation can have a detrimental effect on electrical equipment and dosing tubing. In these cases, it is crucial to wipe down and clean up the equipment.
How Often Should I do a Partial Water Change?
How often to perform a water change is the big question. This answer is determined by two factors.
How many nitrates and phosphates are in the water
How many micro and trace elements have been used up
When your tank is overstocked, the nitrates and phosphates build up fast and water changes should be done weekly. For most of us, a 20 to 30 percent water change every 7 to 14 days is appropriate. However, this schedule is extremely relative.
If your aquarium is full of fish, live plants, or coral in saltwater tanks, there are multiple elements such as calcium, carbonates, magnesium, iron, potassium, and many other trace elements that are used up and absorbed by the livestock. With saltwater aquariums, many of these are replaced with new, freshly mixed saltwater. With freshwater systems, these elements are usually added separately and don’t rely as heavily on water changes to replace.
Elevated Nutrients
Nitrates and phosphates are two major elements we measure when deciding if organic nutrients are elevated enough to require a water change. This is because most organic material breaks down into various forms of nitrogen and phosphorus. The end result of the nitrogen cycle is nitrates (NO3) and Nitrogen (N). The end result of phosphorus binding in fresh and saltwater is phosphate (PO4-).
In addition to elevated nitrate levels being toxic to fish, these nutrients can also contribute to unsightly algae growth when left unchecked. However many days after your last water change it took for your nitrates to rise above 20 ppm is a good schedule to perform water changes.
There are some types of biological and chemical filtration that can reduce nitrates and phosphates, giving you a little more time before a water change needs to be done to reduce organic nutrients. But these filtration methods won’t help when it comes to replenishing elements and compounds used by the animals in your aquarium.
Expended Macro, Micro, and Trace Elements
Freshwater
When I change the water in a freshwater aquarium, I start with pure RODI water. I then add back in calcium, magnesium, and carbonates as necessary for the specific aquarium. In a freshwater system, calcium and magnesium are not generally used up by the animals or plants. However, the carbonates can diminish if there is a strong microbiome.
The elements which would need to be replaced regularly are normally the macro, micro, and trace elements used by plants.
Nitrogen
Phosphorous
Potassium
Iron
Trace Elements
These are normally added by dosing the aquarium as needed, usually right after a water change and then halfway before the next one (once or twice weekly).
For freshwater aquariums, or planted ones at least, the new water does not normally replace all the other elements, just the calcium, magnesium, and carbonates, which were removed during the RODI filtering process.
Water changes on planted tanks do help reset the fertilizer or macro, micro, and trace element levels as well.
Saltwater
Anytime a water change is performed on a saltwater tank, the new water is always mixed with a “salt mix”. This is a formulated mixture of around 80 or 85 percent sodium chloride and approximately 15 percent calcium, magnesium, carbonates, and other elements.
Unlike freshwater aquariums, saltwater animals such as coral, utilize nearly all of these elements (except sodium chloride). In between water changes, all these vital elements are slowly decreasing as the organic nutrients (nitrates and phosphates) rise. Performing a partial water change not only reduces toxic organic nutrients, but also replenishes the vital elements at the same time.
Some saltwater aquariums are stocked heavily enough where they need to add even more of these vital elements in between water changes. This is called dosing, similar to what freshwater plants require with their fertilizers.
Partial Water Change as a Solution
In many cases, but not all, a partial water change can help fix a problem or set your aquarium back on track. Oftentimes we experience a symptom of unhealthy livestock and don’t know exactly what is causing it. When in doubt, a series of small (10 percent) water changes every few days can help bring an ailing tank back to life.
Every Aquarium is Different
Over time, the optimal schedule for cleaning your aquarium will become apparent. Check for the following signs to determine your aquarium’s maintenance schedule.
Is my mechanical filtration dirty, and slowing or clogging water flow from the filter?
Is my aquarium water tinted yellow?
Are the chemicals I’m trying to remove with chemical filtration trending upward again?
Is the aquarium glass covered in algae?
Is the equipment inside and outside of the aquarium forming salt creep or hard water stains?
Are my nitrates above 20 ppm?
Are the vital elements trending down below safe or useful levels?
You may have only answered yes to one or just a few of these questions. You don’t need to perform all your maintenance duties simultaneously. Some aquariums need their filtration changed weekly and the water changed biweekly, while others may need everything done once a week. Every aquarium is different.