How Often Should Your Aquarium Water Be Changed

How Often Should Your Aquarium Water Be Changed

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Water changes are crucial in any aquarium environment with live animals and plants in it. Adequate changes help keep toxic chemicals such as ammonia and nitrites out of your fish tank for a healthy colony of aquatic pets.

In general, it is recommended to do 10 to 15 percent water changes every week in an optimally stocked fish tank. For heavily stocked aquariums, especially those with fishes that give out a big bioload, bump up to 20 percent each weekly.

That said, you’re fish will do Ok with 25 percent water changes every two weeks in a lightly stocked fish tank with a lot of plants and adequate filtration.

Read on for more insight.

Can You Change Your Aquarium Water Too Much

There is not an exact amount of water you should change in a fish tank, but changing too much will cause a lot of stress on your fish and even kill some.

Becacause the water is the fishes' primary home, and the animals depend on it for survival, some level of uniformity is paramount. You only want to change an amount that won’t abruptly vary the temperature, ph, and mineral level of your water to the extent of stressing your aquatic friends.

To top that, I recommend preparing your water before doing any change to make sure the setting and parameter are akin to what you have in your fish tank, more so the ph and temperature setting.

Dechlorinate water from municipal sources is also advisable since it’s often treated with chlorine to make it safe for humans consumption, but not necessarily so for aquarium fish.

Having said that, there are times you might need to do a full (90 to 95 percent) water change in your fish tank. For instance, if you have significant algae or snail problem or widespread infection such as ick.

Can You Do A Complete Water Change in A Fish Tank

Start a new tank, cycle it properly, then transfer your fish over while acclimating them properly is the only sure 100 percent aquarium water change🤷‍♀️.

A full 100 percent water change is never a good idea for any fish tank even when the goal is to expel contaminating elements such as algae, pest snails, and infectious pathogens such as ick.

Even so, a significant aquarium water change (up to 75 percent) is not entirely unheard of. In fact, it’s been implemented successfully by more hobbyists than you might think.

You just need to take a few precautionary measures, such as not exposing your filter and substrate to the air. This ensures beneficial bacteria remain alive and keep your cycle from stalling.

Considering other solutions to the challenge you are facing as an alternative to a full water change is also recommended; only take the complete change route as a last resort.

For instance, if you are dealing with an algae issue, consider starving them of light by only leaving your bulbs on for a maximum of 10 hours a day. You can also try expelling nutrients that help algae thrive, including nitrates and phosphorus, by adding live plants and refrain from overfeeding your fish.

Most importantly, conduct weekly 10% partial water changes or 20% every other week. This is because, in the absence of plants, nothing else will absorb the nitrates produced by the nitrogen cycle, except algae. Even with plants, such neglect will severely elevate the nitrate levels.

In case of pest snails, try using snail traps or adding fishes that will eat snails.

Cleaning your gravel, plants, driftwood, decorations, and aquarium glass also goes a long way in keeping snails and algea at bay.

One last thing to consider before you settle on a complete water change are partial replacements staggered over some length of time.

I would do 30 to 50 percent water changes, wait a couple of hours to a day, then do another replacement while being careful to match the temperature, ph, salinity, and GH levels to those the fishes are accustomed.

How to Do A Full “100 Percent” Water Change in A Fish Tank

If you are doing a “100 percent” water change, chances are all the parameters will considerably disturb, which will, in turn, shock the fish’s body, and may even cause them to perish within a few hours of adding the new water.

As I mentioned, note that changing the water in your fish tank 100 percent is not feasible as this would mean starting the whole process altogether; probably even cycling your fish tank afresh.

This is true even if your goal is to replace severely contaminated water.

So, the best thing to do would be to change 50 to 75 percent of the water and make sure your substrate and filters remain untouched to keep beneficial bacteria alive.

That said, to successfully implement a “full” aquarium water change, you would first need to have enough water of the same temperature, ph, and other parameters to match the water your fishes are accustomed.

If you do not have a problem with starting your setup altogether, you will also need to have an equally sized spare tank to hold your fish while the old one cycles.

A temporary holding tank is also helpful because it will hold your fish in case the replaced water causes changes to the parameters of your aquarium to the extent of harming your fish.

This includes changes in ph, GH, salinity, hardness, and temperature caused by the new water.

If you are doing a 100 percent water change, chances are all parameters will considerably disturb, which will, in turn, shock your fish’s body, and cause them to perish within a few hours of adding the new water.

Once you are ready to do the water change, use a siphon or pump to get most of the water out, making sure you leave enough to cover your fish.

Angels, discus, and other species with odd-shapes will often end up with their sides partly uncovered, but as long as they are not visibly struggling, they’ll be fine. Besides, the replacement should only take a quick minute.

Once you’ve expelled enough water, start the refill process with the water you prepared before emptying your tank. Even so, you want to make sure the parameters are stable and akin to what your livestock is accustomed to.

Add a conditioner, de-chlorinator, and for fishes like mollies and African Rift lake Cichlids that love things on the harder side, add the appropriate cichlids' salts as your tank fills.

For a short while, your fishes will most definitely be stressed, but they should start acting as expected by the time your tank is half full.

Some fish keepers advise that you clean your filter media with water changes, but in this case, I do not recommend washing or changing your filter media, unless it’s evidently filthy or harboring some of the elements that justified the change in the first place.

When To Do A First Water Change in A New Fish Tank

A common misconception in the hobby is that you should not do water changes while your tank is cycling to avoid disturbing the bacteria colonies developing in the filter.

However, the truth is not only does performing frequent, small water changes in cycling aquarium not delay or hamper the process, quite often appears to turbocharge it.

Besides, if doing fish-in cycling, failure to perform adequate water changes will result in ammonia poisoning and killing even your hardiest fish. Remember, all this while your biological filters won’t be working at full capacity, so even small amounts of toxins are lethal to any aquatic animals in the tank.

That said, there are varying schools of thought as to how much (and when) water changes to do. Even so, most hobbyists agree it should be anywhere from 10 to 35 percent water changes every 1 to 2 weeks.

An equally effective rule of thumb is to start with a 25 percent water change after the first 15 days, then stagger the rest between 10 and 20 percent every 2 weeks until your fish tank is fully cycled.

How Often Should You Change Water in A Fish Bowl

Fish bowls are quite popular among young, beginner fish keepers, especially those with no much room for larger fish tanks. But bowls have an Achilles heel, in that get filthy very quickly and can only hold a single tropical fish.

As such, a fishbowl will often require more frequent water changes and cleaning. Ideally, you should clean yours and replace 10 to 20 percent of the water once or twice every week.

You’ll also need to stay on top of the parameters because they may turnabout erratically from ideal to filthy in a short minute.

Also, please note that a fishbowl is not ideal for keeping any tropical fish, including goldfish and betta, so if you have one, I highly recommend getting at least a 10-gallon aquarium for the health and safety of your fish.

Thats all. Happy fish🦐🐠 keeping.

Eddie Waithaka

Resident Content Creator and Marketer at AquariaWise who talks about aquariums and fish and aquascapes a lot.

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