How to Change the Water in Your Freshwater Aquarium the Easy Way

Eric is an aquarium enthusiast with over two decades of experience caring for
a wide array of tropical fish.

Regular water changes are the best thing you can do for your freshwater
aquarium, but do them the easy way!

The Best Way to Change Aquarium Water

The weekly water change is the most important thing you can do to make sure
the fish in your freshwater aquarium remain happy and healthy. Unfortunately,
it’s also a step that some aquarium owners tend to overlook.

When life gets busy, fish-tank maintenance is often put on the back burner to
be addressed later, or forgotten about altogether. Fish can die due to poor
conditions, and you may end up feeling like this whole aquarium thing is more
trouble than it’s worth.

This article will cover a quick, easy and painless way to keep your aquarium
water clear and healthy without spending an hour or more cleaning every week,
and without spilling water all over your carpet.

Remember that no aquarium out there requires zero maintenance but, with the
right tools and planning, a lot of the hassle can be minimized.

It’s a good idea to perform a deep cleaning of your tank about once a month,
or at least every other month. This means taking out all the decorations (if
you don’t have live plants) and cleaning them, dealing with any algae issues,
cleaning the filter, and vacuuming the gravel. But these cleanings are very
stressful for your fish.

A weekly water change doesn’t need to involve all of that and can be
relatively stress-free for both you and your fish. Keeping up with your fish
tank maintenance schedule shouldn’t be something you dread!

How to Change the Water in a 10-Gallon Tank

If you have a small 10-gallon setup your weekly water change will literally
take you minutes. You’ll need a small mini-siphon gravel vacuum. I recommend
the Python Pro Mini. It’s inexpensive, easy to use, and in addition to a
bucket, it is really all you need to change the water in a 10-gallon tank.

Please note: Any bucket you use for your fish-keeping hobby should be
designated “fish only”. Never use a household cleaning bucket for working with
your fish tank as any residual chemicals will be harmful to your fish.

To change the water in a 10-gallon tank, simply use the mini gravel vac to
siphon water from your tank into the bucket. Never remove all of the water;
only take about 30%.

A good way to measure this, aside from eyeballing the tank, is to find
yourself a 3-gallon bucket. When the bucket is about full you know you’ve
taken enough water. Discard the old water, fill the bucket with fresh water,
pour it gently into your tank and your water change is done.

Water Changes in Big Tanks

For those with big tanks, the job gets much more complex. If you want to, you
can use a siphon and repeatedly fill and empty the bucket, then repeatedly
refill your tank with the bucket.

This method may require a dozen or more trips back and forth between your tank
and the water source. It’s time-consuming, back-breaking, and messy, not to
mention a really good excuse for taking up a different hobby. But there is a
better way:

There are water-change systems on the market that drain the water straight
from your tank to your sink. These systems involve a long tube that hooks up
to your kitchen or bathroom faucet on one end and has a gravel-vac fitting on
the other end.

You can siphon water from the tank and send it directly down your drain. When
the tank is drained to the desired level, simply throw a lever and the tank
begins to fill.

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Sound easy? It’s definitely way better than carrying that sloshing bucket
around. Here’s a look at how I use a water changer to do quick and easy weekly
water changes.

Water-change systems hook right onto your faucet for easy draining and
refilling of your fish tank.

Step 1: Set Up Your Water Changer

Water changers are designed to hook up to your kitchen faucet or similar water
source. When in draining mode this hookup sends the dirty tank water right
down your sink drain.

I use mine a little differently, though. Water changers come with tube lengths
up to 50 feet, more than long enough to stretch to and out the door in most
homes. I like to send my dirty tank water out onto my lawn instead of letting
it go down the drain.

In the summer, I use it to water flowers and plants. This is just an effort at
a little conservation on my part and certainly not necessary.

Whatever you choose to do with the old water, a water-change device makes it
simple to siphon water from your tank and send it on its way.

Note: Throughout this article, I’ll be using the Aqueon Aquarium Water
Changer. I use the 50-foot model, which I prefer because of the way I drain
the water (as explained above). However, the 25-foot version is fine if it
will reach your sink.

As long as you secure the end of the hose in your tank, you can do something
else until the desired amount of water is drained.

Step 2: Drain Water from the Tank

After you’ve set up your water changer as specified by the manufacturer all it
takes is a flip of a level for water to begin to drain from your tank. Keep in
mind that the purpose of the water changer is not only to siphon water but
also to clean the gravel.

We’re not going to make use of the gravel-vac function for our super-easy
water change, but you should use it when doing your monthly deep cleans.

Water changes should always be partial water changes. Again, we’re only
going to take around 30% of the old water out of the tank. You should never
replace all of the water in your aquarium at once. While water changes are
healthy for the fish, very extreme water changes can actually cause them a
great deal of stress and possibly even kill them.

Remember, the reason you are changing the water in your tank is to dilute
the natural waste made by the fish and uneaten food. In the wild, this happens
by the natural actions of the streams and rivers where the fish live. In your
tank, you need to do it yourself with water changes. As the saying goes:

The solution to pollution is dilution.

Water changes do not take the place of regular tank cleaning and maintenance,
but they do help a lot when it comes to controlling waste in the tank, and
even preventing algae growth.

There is no need to remove the tank lid. You don’t even need to turn your
filter off as long as the intake is low enough in the water that it can
continue to function.

You do want to make sure your heater is low enough in the tank that a
significant portion of the heating element is not sticking out when the water
is drained to its lowest point in the process.

If you have little fish in your tank you’ll want to keep an eye on them so
they don’t accidentally get stuck in the tube.

Watch Out for the Little Fish!

It will take a few minutes for the water to drain out and you really can’t do
much but watch. Be aware that the tank-end of the tubing may pop out on its
own, so you may want to wedge it between decorations so it stays put. If it
seems secure, while the water is siphoning you can go and do something else
for a few minutes.

However, if you have small fish in your tank you’ll want to keep a close eye
on the open end of the tube that’s in the aquarium. Make sure they don’t swim
up and into the tube where they can get stuck.

Yes, it can and does happen!

Healthy fish, even little ones, should be plenty strong enough to escape the
pull of the siphon. The problem is, fish aren’t very bright. The suction may
cause little bits of debris to dance around inside the clear, plastic opening
of the tube. Small fish may swim in chasing the debris and get stuck if you
aren’t careful.

Take the water level down only about 30%. Notice the filter is still running
and only the top of the heater is poking above the low-water level.

Step 3: Refill the Aquarium

Refilling the tank with a water-change system is just as easy as emptying it.
Make sure you have a strong connection between the tubing and the faucet
receptor, otherwise water can burst everywhere.

You will want to close the lever on the tank-end of the tube before going over
and flipping the “fill” lever at the faucet. When you return to the tank, flip
the tank-end lever back to open and the water will start to flow.

Again, if you can secure the business end of the tube in the tank you can
leave it while you do something else. But don’t forget about it or you’ll end
up with a flood! I use a timer with an alarm to remind myself, and, yes, I
learned this the hard way.

Fill the tank just to the bottom of the filter outlet to allow water movement
without too strong of a current.

Note: I get a lot of questions asking why I didn’t add a de-chlorinator
or water conditioner at this step. That’s because my water source is fresh,
country well water. It is somewhat hard, and thus naturally slightly high pH,
but I’ve never used any additives or chemicals to adjust it. However, if you
use a municipal water source or some other water supply that requires
treatment you will need to treat your tank at this point.

When you flip the lever, water will flow from the gravel-vac end just like a
garden hose.

Water Temperature

One of the big questions when refilling a tank concerns the temperature of the
water. Of course, tropical fish require temps in the mid-to-high 70s to be
happy.

But since you are only changing around 30% of the water you can get away with
adding cooler water to the tank; there is no need to try to match the water
temp exactly.

I prefer to add cool water because of the way our water system heats water in
our house. Cold water travels straight from the well to our tap, where hot
water takes a lap through the water heater.

I prefer my fish get the purest water possible so I try to avoid as much
heated water as I can. Note also, there is a big difference between cooler
water and cold water. Never add ice-cold water to your tank. For some fish
species, a temperature drop of as little as fifteen degrees can be deadly.

You might also notice that a burst of cooler water will invigorate some fish
in your tank, and they may seem especially spunky after a water change. To
them, a sudden influx of cool, fresh water simulates the start of the rainy
season.

See the Aqueon Water Changer in Action

How Often Should You Change Aquarium Water?

Weekly water changes are a great idea, but they do not take the place of
monthly or bimonthly deep-cleanings of your tank. You still need to vacuum the
substrate and get all of that waste out of the gravel, clean the sides of the
tank of any algae buildup, clean your decorations to keep them looking bright,
and perform regular maintenance on your filter system.

But these deep-cleanings can be stressful for the inhabitants of your
aquarium, so regular water changes go a long way toward keeping your tank
clean without freaking your fish out too often.

A water changer is a great tool for making water changes quick and easy. Once
you have a little practice you can perform the maintenance described in this
article in as little as twenty minutes, and you can spend much of that time
working on other household tasks while your tank drains and fills.

No more carrying buckets around the house, and no more spilling water on your
carpet!

Taking care of a tropical aquarium does take a little work, but it’s always
better to work smarter than harder. Using the right tool for the job will mean
you’ll have less dread for aquarium maintenance, and can enjoy your tank more.

Have fun, and here’s to many years of happy, healthy fish!

Hooray! It’s the rainy season! Third time this month!

This article is accurate and true to the best of the author’s knowledge. It
is not meant to substitute for diagnosis, prognosis, treatment, prescription,
or formal and individualized advice from a veterinary medical professional.
Animals exhibiting signs and symptoms of distress should be seen by a
veterinarian immediately.

Comments

Eric Dockett (author) from USA on July 31, 2020:

@Katherine – I’m not sure what you mean. Are you saying your tap water has all
of that in it?

Depending on how bad it is, you can try treating the water in the bucket
before adding it to the tank. I would test the water throughout the process
the first time to make sure it was safe.

How are you adding water to your tank now?

Katherine Canon on July 30, 2020:

I wish there was a way to add water from the bucket to the tank. My water is
horrible. It has ammonia, nitrates, nitrites and high ph. If I added that into
my tank is probably kill the fish before the water conditioner and quick fix
(get rid of the ammonia and nitrites) have time to do their job.

Eric Dockett (author) from USA on March 11, 2020:

@Maddie – Aside from the water change device? No. You dig the end of the water
changer into the substrate and it pulls debris out of the gravel as it works.
I was only demonstrating a quick water change in this article, but if I were
doing a cleaning that’s how I’d do it. You may occasionally need to remove
debris with another tool or your hands if the siphon isn’t strong enough to
pick it up.

Maddie on March 10, 2020:

To clean the substrate, do you need an additional tool to do so?

Eric Dockett (author) from USA on February 03, 2020:

@Robinson – You can try different foods and even different lights for the
tank. You also may want to look at stress levels in the tank. Stressed fish
sometimes lose their color.

Robinson1224 on February 01, 2020:

How can I get my Cichlids to color up

Eric Dockett (author) from USA on August 16, 2019:

Hi Danielle – It’s a good idea to research the nitrogen cycle in aquariums so
you can better understand all of this. Letting the water filter for 7-10 days
is a gross oversimplification of what needs to happen before an aquarium is
ready for fish.The aquarium needs to “cycle” so the healthy bacteria colony
builds up to a point where it can manage all of the waste your fish are going
to produce.

When you do a partial water change you reset that process to a small extent,
but not drastically. There is no reason to prepare water ahead of time. When
you treat water you can dose the whole tank, even though you are only adding a
fraction of the total amount.

Hope this helps. Good luck!

Danielle on August 15, 2019:

A question about adding the new water. Is the new water ready to be poured
into the tank right away or does the chemical take a day or two to do it’s
job? When setting up our new aquarium the directions read to “let it filter
for 7-10 days before adding fish”. Wondering if I should prepare a bucket of
“new water” to use days ahead of time? thx

Eric Dockett (author) from USA on March 18, 2019:

@Eric – Yes, If your water source has chlorine or other chemicals in it you
need to add conditioner to new water you introduce into your tank.

Eric on March 17, 2019:

Do I need to add water conditioner for the ten gallon water change?

Eric Dockett (author) from USA on March 14, 2019:

@muscleguy32 – 30% is a number I’ve always used. It’s easy to eyeball about
1/3 of the tank. If I have live plants I do smaller and/or less frequent water
changes. I try to keep it pretty basic.

muscleguy32 on March 14, 2019:

Where do you get 30% from. Every other advice I’ve ever seen or used myself in
more than 40 years of fishkeeping is 20%. I live in Scotland and our tapwater
in the winter is COLD.

This is a problem because cold water has more gases dissolved in it. If you
mix cold water with warm those gasses can come out and in the form of tiny
bubbles in the fishes’ gills. It’s the fish equivalent of the bends in human
divers.

The only time I would use a python style device would be if I also installed
an RO water unit as the water out of that is slightly warm.

After each water change I fill a 2G bucket with a lid (for my 10G tank) so it
can warm up to room temp and de-gas. Since I run blackwater tanks it also
enables me to add tannin producers to it and let them soak for a week.

Also remember a tank may be nominally 10G but remember your Archimedes
principle, all that gravel and driftwood and all those plants etc take up
volume. So my nominal 20% becomes closer to 30% in terms of the water volume.
But it is safer to to the calculation on the nominal volume of the tank since
the amount of added stuff varies.

Eric Dockett (author) from USA on January 10, 2019:

@Whitney – I have never seen one like that, though I’ve often thought it would
be a great idea.

Whitney on January 09, 2019:

Are there any versions of these syphons that would work with a retractable
sprayer style faucet?

Eric Dockett (author) from USA on December 23, 2018:

@Susan – Unless you are getting the gravel from nature there is no need to
boil it. Aquarium gravel from a fish store should only need to be rinsed. That
tank is too small for one betta let alone two, which is likely why you lost a
fish. The film is probably algae, which can thrive when there is excess food
and/or waste.

Susan on December 22, 2018:

I have 2 Bettas in the same tank with a divider. I condition the water and
clean the tank completely every couple of weeks. It’s a 2.5 gallon tank with a
filter. However, i notice a real gross rust color film on the walls of the
tank. I even boil the gravel in hot water to sanitize and clean the gravel. I
recently had what appeared to be a very healthy Betta die. What is causing
this?

Eric Dockett (author) from USA on September 11, 2018:

@Linda – I don’t know if it presents any specific health concerns, but it is
pretty gross. I wouldn’t do it. That strainer touched all kinds of nasty stuff
decaying in the rocks, including fish waste.

Another reason I wouldn’t do it is for the health of the fish. Washing their
utensils in dish detergent presents the possibility of introducing
contaminants into their tank. Not good.

For the safety of humans and fish it is a smart to have a separate set of
tools for fish tank use. He can make sure the items he uses are safe for the
fish, and the humans in the house can be sure the strainer that just prepared
their pasta hasn’t touched fish waste.

Linda on September 10, 2018:

My son uses a strainer to catch the rocks when he dumps the water out of his
small fish bowl. He then washes the strainer and uses it for family uses. Is
this healthy?

Eric Dockett (author) from USA on September 08, 2018:

@Ethen: Here is an article that discusses reasons for cloudy tank water:

https://pethelpful.com/fish-aquariums/Cloudy-Fish-…

Performing water changes without a siphon is tricky. You’ll have to scoop it
out with a cup or bucket. It is a good idea to find a way to get a siphon,
though. Not only is it easier, but vacuuming gravel periodically keeps the
tank much cleaner than simply changing the water.

Ethan on September 05, 2018:

Hey my water is like milky or foggy and its just been maybe a month first is
that normal 2nd i dont have that tool nor can i get it how would i go about
changing the water normal without the tube thing

ben on May 22, 2017:

I would like to use the same water changing method. but both fausets in my
house are not threaded. or have an attachment already on them that i cannot
remove.. guess im stuck with the bucket method

Eric Dockett (author) from USA on January 22, 2017:

Hi Melissa. I don’t like using chemicals either, unless it is absolutely
necessary. Since you said your fish are healthy, I don’t think you are at that
point yet.

I would carefully remove the plants from the pot. You may want to cut them out
so you don’t tear up any of the roots. And yes, they will grow in gravel.

If you buy the kind of plants with roots that come in that jelly-like glob
stuff you want to make sure you rinse all of that away before planting.
Typically that kind of plant does not come in a pot.

Good luck!

Melissa on January 21, 2017:

Hi thank you for replying. I do about a 20% change. No I haven’t tested the
tap water itself I will do that and let you know.

There is just two small fish in the tank. I will get some live plants when I
go to the pet shop next. Will the plants be ok in a gravel tank? Is it best to
plant them or leave them in their pots I really appreciate your help. I went
to pet shop and they wanted to sell me some chemical to remove the ammonia I
don’t like using chemicals in my tank so I didn’t buy that. It’s only showing
up slightly on the ammonia strip reading just 0.25. I use the liquid testing
strips.

Eric Dockett (author) from USA on January 21, 2017:

Hi Melissa. First thought: Tap water itself can sometimes contain ammonia.
Have you measured the readings for your tap water and compared them with what
you are seeing in the aquarium a few days after a water change? This will help
you diagnose whether or not the problem could be the water source itself.

Other thoughts: Your tank could be overstocked. Or, the water changes you are
performing are too large and frequent and it is negatively impacting the
beneficial microbe colonies in the tank.

If you don’t already have live plants consider adding a couple. They can help
with ammonia levels, particularly if the tank is slightly overstocked.

You didn’t mention the percentage water change you do every week. I wonder if
you reduced the amount of water you are changing or switched to every-other
week this would help with your microbe colonies. Obviously you’ll want to
monitor your water parameters closely as you experiment with different ideas
here.

Good luck! I know it is frustrating but at least your fish don’t seem to be
suffering from whatever is going on.

Melissa on January 21, 2017:

Hi, I always seem to have a small amount of ammonia in my tank. I do weekly
water changes I Let the water sit overnight with tap safe before I use it. I
just can’t seem to get the ammonia down. All my other levels are spot on. I
siphone the gravel. My fish are really healthy but worry as I know even a
small amount can harm them. It’s a 90 litre tank. Any advice on ammonia?

Eric Dockett (author) from USA on October 28, 2016:

Hi Chris: I’m sorry, I’m afraid I don’t know much about caring for turtles. It
seems a water changer/gravel vac would work fine, just like in a fish tank. As
for watering the plants, I don’t hook up the water changer to an outside
spigot. It’s long enough that I can run it out the door to the plants on my
deck when I am draining the water. This might not work for everyone,
obviously. Good luck!

chris a on October 27, 2016:

Hi. My daughter has a turtle tank and was wondering if this system would be
good to use in the tank we have. 55 gallon tank. Oh and you say in summer you
water your outside plants. Do you attach this to an outside spigot?

If this can be used in her turtle tank do you recommend taking out the turtle
while doing the water change? Then putting her back in when the water up to
the temp it needs to be. Sorry for tons of questions. My daughter will soon
leave to college and I will be responsible for the maintenance and I am just
trying to find an easier way to do this 🙂

Eric Dockett (author) from USA on April 30, 2016:

Hi Madalynn. You do not need a gravel vacuum just to change the water. You can
use a tube as a siphon, or even just a bucket to remove water from the tank
and replace it. However, gravel vacs are much more convenient and easier to
use, and you can clean the gravel as you change the water if you wish.

Madalynn Walden on April 29, 2016:

Do you need a gravel vacuum to change the water?

Eric Dockett (author) from USA on December 19, 2015:

I agree tanner. That’s one of the reasons I use the hose as a simple siphon
rather than of doing it per the directions that come with the water changer. I
don’t leave the water running the whole time.

tanner on December 18, 2015:

This is a good idea, however, I think that this is a HUGE waste of water being
that the water is running while your cleaning the tank.

Eric Dockett (author) from USA on March 02, 2014:

Hi Chris. Personally, I don’t add anything to my water, since it comes from a
well. If you are using municipal tap water you should consider adding
something to handle the chlorine or anything else that might be in there. My
philosophy it always to add as few chemicals as possible, so only use what you
really need.

chris on March 02, 2014:

Do u add tap safe

Eric Dockett (author) from USA on July 03, 2013:

Yeah Marion, it really changes your life when you realize these water changers
exist! No more carrying buckets and getting the floor all wet. Everything is
super easy, even for really big tanks. Thanks for reading!

marion langley from The Study on July 03, 2013:

I didn’t know the water to sink changer tool existed. Have had a number of
freshwater tanks…enjoyed the bigger ones more…cleaning seemed to take the
same time and the bigger ones stayed cleaner longer. If I ever opt in for the
100 gallon tank I gotta look into getting one of those tools! Thanks for
writing.

Eric Dockett (author) from USA on June 24, 2013:

Hi Nate. Fortunately that’s not a problem I have to face, since I use well
water. What you can do is gradually add the dechlorinator to the inflow of the
water as the tank refills. You can dose the whole tank volume, not just the
water you’re adding. Hope this helps!

NATE on June 24, 2013:

What about dechlorinating your water when your filling the tank back up using
this method?

Eric Dockett (author) from USA on June 11, 2013:

Thanks jdw!

John David from Middle America on June 10, 2013:

Quite helpful, thank you! Thumbs up!!

Elliott on April 26, 2013:

Thanks. Very helpful. Yes, local fish keepers is a good idea. It’s not
midsummer yet, and last time I did a water change it came out at 93 degrees.
My only idea was to fill a bucket and let it sit for half a day so it’s at
room temp. Then I would use another bucket to drain the old water and make the
change immediately. Sure would be nice to make one of these simple systems
work.

Thanks for the suggestions. I like the idea of ice bottles as an alternative
for now.

Eric Dockett (author) from USA on April 26, 2013:

Hi Elliot. This is indeed an issue, as 100 degrees is too warm to add directly
to the tank. I can think of a few creative suggestions, like perhaps carefully
offsetting the warmth of the water with ice packs (frozen plastic bottles
filled with clean water) but maybe there is an easier way. Id start by calling
or visiting a local aquarium shop and asking them if they have any advice. If
100-degree tap water is common in your area, I’m sure they’ve had the question
before. Good luck!

Elliott on April 25, 2013:

What if the tap water comes out hot all the time? I live in AZ and in the
summer the tap water from the cold faucet can be nearly 100 degrees.

Eric Dockett (author) from USA on January 04, 2013:

Thanks moonlake! I did the bucket method for a long time before I decided to
get one of those water changer things. Way easier!

moonlake from America on January 03, 2013:

I loved my aquariums when we had them. We changed the water pretty much the
way you changed yours. Now we have just two gold fish and a beta. Their little
bowls are pretty easy to change. Good information and your tanks look great.