How To Drain A Fish Tank The Fast & Easy Way

    How to drain a fish tank

    Filling an aquarium is the start of something wonderful! But what if you have to do a deep cleaning or need to move the tank? All of that water has to go somewhere…So how do you drain a fish tank easily?

    Draining a fish tank is similar to doing a large water change. You shut down all of the technology running on your aquarium. Next, you catch your fish and bag them up. Then you use a siphon hose to remove all of the water. Last, the tank either gets put away or is refilled.

    Not everyone feels 100% comfortable following written instructions. So I’ve also included this great video that demonstrates how to drain a fish tank right here:

    YouTube player


    How To Drain A Fish Tank

    How to siphon a fish tank

    Draining a fish tank is simple and only requires a few tools!

    Supplies Needed

    • Mats or Towels to clean up spilled water
    • Siphon Hose (gravel cleaner)

    Whichever method you choose to drain a fish tank, don’t forget to pick up some aquarium fish bags for transportation. These are just like the ones the pet store gave you to bring your fish home.

    Only add water 1/3rd to 1/2 of the volume of the bag. Never fill the bag entirely with water. Fish need oxygen and the air holds around 100 times as much oxygen as water does.

    If you leave no air volume in the bag the fish will use up all of their air and suffocate. Keep the water in the bags warm as well by placing them inside a small cooler. A bundle of blankets or towels can also work if the move won’t take too long.


    Step 0: Set up mats underneath the area where you plan on moving buckets and bags of fish. Spills can easily occur. Mats, towels, and even a little newspaper will go a long way towards keeping the room tidy.

    Step 1: Remove all of the fish, plants, corals, or invertebrates from the aquarium. Place them inside aquarium fish bags, taking care to add no more than 50% water and 50% air.

    If you expect it to take longer than 30 minutes to get your pets to their new home, place them inside a cooler. A cooler will maintain the proper water temperature in the meantime.

    Step 2: Disconnect all of the devices attached to the aquarium. The aquarium lights, heater, filter, and other devices should not be kept running during the draining process.

    If the water level gets too low, devices that pump water can burn out. The magnetic impeller pumps that run filters are usually water cooled.

    Heaters that are left to run will cause the protective glass to become searing hot. If you brush against the heater, you will get a small burn. Also, a splash of aquarium water can cause the hot glass to shatter.

    Step 3: Place the fish tank water bucket near the tank but below it if you are using a gravity powered siphon hose. You can also use a water pressure powered siphon hose that run directly into your sink.

    For gravity vacuums, simply add enough water to get it flowing out of your freshwater tanks. Run it through the gravel at the bottom of the tank to remove debris and clean it.

    Step 4: Once the aquarium is empty, you can save the buckets of water for various household uses. Or you can dump them directly down the sink drain, shower drain, or even a nearby toilet.

    But I recommend re-using aquarium water, if at all possible! Only use clean water, not the buckets that have a lot of fish poop collected at the bottom.

    If the aquarium is to be put away, then it’s time to scoop out any gravel at the bottom.

    Step 5: Either put away your drained fish tank, if you aren’t planning to re-use it. Or you can start refilling the aquarium with treated tap water.

    Should A Fish Tank Be Completely Drained?

    This depends on the purpose you have in mind. I’d only ever completely drain a fish tank if I were intending to put away the aquarium forever.

    I don’t recommend draining a fish tank only to clean it. It’s stressful for your fish.

    Plus the organic matter that accumulates in a tank is good for plants, your beneficial bacteria, and your pet fish. Weekly water changes are best if you want to keep your tank clean.

    Should You Remove Fish When Draining The Water From The Tank?

    The size of the tank and the number of fish determines whether you should remove them before or after draining the tank. If you have a small aquarium, then remove the fish first.

    The fish won’t be that hard to catch. Plus there is a chance they might get taken up in the siphon hose. While they won’t usually be injured, there is a small chance they are harmed by the ride into a bucket.

    Fish with spines like corydoras can even get trapped in the hose. Which definitely elevates their already high stress levels. So don’t use a siphon hose to replace a proper net.

    What if you have a larger tank with fast-moving fish? Start the draining process until the water level is low enough to catch your fish easily. Then drain it the rest of the way.

    How To Remove Fish From The Tank

    A fish net is all you need to catch aquarium fish. Keep your fish healthy by not touching your pets as much as possible during the moving process. Not even inside of the net.

    Fish have a coating of protective materials like mucus that keep them safe from bacteria and toxins. The germs and oils on your hands are bad for fish.

    How Often Do You Need To Drain A Fish Tank? 

    As long as you do a partial water change every couple of weeks, draining the tank should not be necessary. But there are times where you have no choice but to pull out all of the water:

    Preparing To Move The Fish Tank

    You should almost always drain all the water from an aquarium when you are planning to move it. Maybe you want to move the aquarium to a new stand, room, or home. In all cases, it’s safer for both you and the aquarium if you drain water.

    For starters, water is heavy. An aquarium may look manageable to carry. Especially tanks 10 gallons and smaller. But water weighs 8 lbs per gallon. Not to mention any decorations you have inside of it, like gravel.

    Even a 5 gallon tank is a hefty load. If you were to stagger, the weight of the sloshing water will easily take it right out of your arms.

    Capturing Difficult Fish

    Sometimes it’s impossible to capture a fast-moving fish. Especially if they live at the bottom of the tank. And the aquarium is full of decorations.

    Maybe the fish needs to be moved to a quarantine tank for disease treatment. Or it’s a bully that needs to be removed. Draining a lot of the water can make it easier to catch a fish that does not want to cooperate.

    I’d start with trying to lure in a difficult to catch fish with food. Feed as normal but keep the net nearby. Try to catch them on the very first lunge with a large net. Succeeding right then will save you a lot of hassle.

    If the fish escapes, try removing as many decorations as you can first. And if you still can’t catch it, then it’s time to drain water from the aquarium.

    Breaking Down An Aquarium

    Draining a tank is also done when you are breaking down an aquarium permanently. Often it’s time for an upgrade in size for large fish. Or maybe you just need a break from the hobby.

    In either case, you will need to bag the fish up to prepare for their new homes. And then use a siphon hose to remove all of the water before you clean and put away the old tank for good.

    Deep Cleaning

    Draining all of your fish tank water for a deep cleaning is a drastic step. Spring cleaning is not something I ever recommend doing. No matter how dirty or slimy things have become.

    Removing all of the water and decorations to scrub them resets the nitrogen cycle of your tank. If you add all of your fish at once, you are likely to lose some from ammonia toxicity.

    There are other reasons for a deep cleaning, however. Saltwater tank aquarists may find it impossible to control a glass anemone infestation. Or coralline algae has overgrown every hard surface.

    There are few reasons to drain a freshwater tank for a deep clean. Even system-wide issues like green water algae can be controlled through regular maintenance.

    Is It Okay To Pour Aquarium Water Down The Drain Or Toilet?


    Pouring aquarium water down the drain or toilet is fine to do. There are no residual chemicals that will cause issues for municipal water treatment facilities. In fact, tank water is a lot safer for human health than what usually goes down the drain.

    Just be sure that you pace the draining process right. It is easy to pour faster than your drain can take in water. You don’t want tank water overflowing from your sink or toilet bowl onto the floor.

    Other Uses For Aquarium Water

    You can safely dispose of water down the drain during aquarium maintenance. But there are other uses for that fresh water you might want to consider!

    Watering Plants

    Do you have any garden or house plants? If so, put away the garden hose and fill some buckets with aquarium water. Water from a drained fish tank is some of the best you could possible use for plants.

    Fish poop and other debris is rich in organic matter. Which breaks down to release nitrogen, phosphorous, and other plant fertilizers. It also recharges the organic humus found in soil.

    The bacteria that live in your fish tank also enhance the biological activity of the soil. Helping plants grow more vigorously and uptake nutrients properly.

    Don’t try this with a saltwater tank, though. The salt levels are too high and will poison the soil and roots of your plants.

    Refilling A New Fish Tank

    If you are looking to replace an old tank with a new one, save as much of the old water as you can. New water will give you a clean tank. But clean is not what organisms really want.

    Old aquarium water is rich with beneficial bacteria. You can jump-start your cycling process by emptying the old water into buckets. And then using it to refill the new aquarium.

    The old tank water is also already at the pH that your fish prefer. Tap water tends to have slightly different parameters from mature aquarium water. Fish, plants, and other organisms cause it to shift, usually making it more acidic through their activities and waste.

    Just remember to use water conditioner if you don’t have enough water from the old tank. Adding chlorinated water to the old water will kill the microbes you are trying to save.

    How To Properly Refill The Fish Tank After Draining It

    If you aren’t putting away your fish tank for good, then you will need to refill it. If you removed it then your first step is to add your substrate back to the bottom.

    Also, if you have any live or artificial plants then you can get them replanted into the substrate. Make sure that all of your live plants are still wet. Even a brief time spent dry can kill them.

    A garden hose is the most efficient way of filling a drained aquarium with more water. As is a siphon hose that attaches directly to your faucet.

    A bucket is also good; just be ready to take a lot of trips to the faucet. And to get a good arm workout while you’re at it!

    You can add water conditioner either at the start of the refilling process. Or at the end; the conditioner works almost instantly to detoxify chlorine, chloramine, and heavy metals.

    If you have any live plants inside of the tank then its better to dechlorinate at the start. Most plants are quite hardy but chlorine still isn’t good for them.

    Once the tank has been refilled, you need to get the heater running again. Cold water will stress-shock your fish if the temperature difference is 5°F or greater.

    Don’t use hot water either unless you are prepared to let the tank cool. Get the water temperature as close to the desired level as possible before adding your fish!

    Plug in your aquarium lights and filter as well. And once everything is running and the water temperature is ideal, you can add your bags of fish!


    Everyone needs to know how to drain a fish tank. It may seem intimidating the first time around. Especially if you don’t have a smaller tank. But the more often you do it, the faster and less messy it is!

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