5 Ways to Start a Siphon for an Aquarium Water Change - Beginner's Guide Ep: 24

Outside of the aquarium hobby, using a gravity siphon is really not all that common and a skill that most folks just won't naturally encounter or find the need for. That said, it's absolutely mandatory for keeping an aquarium because a siphon is what allows us to remove water from our aquariums easily during a water change. 

When first starting it out, it might seem a little scary because water just comes rushing out of your aquarium through a hose for what seems like no reason at all. The old school fish nerds will tell you "just suck on the end of the tube until water comes out", which nobody in their right mind would do unless you understand how a siphon works.

Trust us, once you get the hang of it, using a gravity siphon is actually pretty easy, comes in super handy, and is not difficult to use by any means.

What Is A Siphon?

A siphon is just one of those things you have to see to fully grasp how it works. By definition, a siphon is a tube used to move liquid upwards from a reservoir and then down to a lower level of its own accord. Once the liquid has been forced into the tube, typically by suction or immersion, flow continues unaided.

When used on an aquarium, you can pull water from your tank without a pump and automatically drain it down into a bucket or container located below. This allows you to remove water easily from the tank, which can then be refilled with fresh, clean saltwater.  This is a water change.

So the siphon device itself is simply a length of tube or hose. We often attach a gravel vacuum on one end of the tube which is a larger diameter, 12-24" cylinder of rigid acrylic and this helps us to more easily pull suspended debris and water from the tank without removing sand and gravel. Technically, any length of vinyl tubing or hose will work to create a siphon. What actually makes the tube assembly a siphon is what happens when you "start the siphon".

How Does A Siphon Work?

A siphon works all thanks to gravity. It starts by filling the siphon tube with water from your aquarium, then positioning the exit end of the tube at a lower level than the entrance end while keeping the entrance end submerged in the aquarium. Once the water is let loose to flow freely downhill, gravity kicks in creating suction and pulling water from the tank down into a bucket or container.

If a siphon is left to run, it will continue to drain water until the two water levels are equal or the tank drains entirely.

The trick to using a siphon is learning how to start it because once you get it going, all you have to do is wait. After the water is drained to the level you need, just pull the higher end out of the water, the tube will drain and the siphon is now broken. So, let's learn how to start a siphon. 

5 Ways To Start A Siphon

 1. The Mouth Method

The most common and easiest method. The siphon tube is filled via suction from your mouth. One end of the siphon is placed into the aquarium, suction is applied to the other end via your mouth until the tube is full of water.  Put your thumb over the exit end of the tube to hold the water inside, then place the exit end into a bucket (lower than the tank) and the siphon will begin to flow.

If you don't stop sucking before the tube is 100% full of water, you will get a mouthful of tank water. This tends to turn some folks off to this method, especially when first starting out. You just have to be careful and most hobbyists get the hang of it after just a couple of starts. After a dozen or so water changes, you won't even think twice.  

2. The Hand Pump

Hand pumps are super easy which is a rubber bulb that is plumbed inline with your siphon.  One end of the tube goes in the tank, the other end in the bucket.  Start pumping the rubber bulb until the tube is filled with water and the siphon begins to flow.

3. Total Immersion Method

You take your entire length of tubing, submerse everything into the tank, including both ends, allowing the entire length of the tube to fill with water. Wrap it into a coil to make it easy and you may need to spin it around to get the water to enter and fill the tube.  Once the tube is full of water, place your thumb over one end, keep the other end in the tank. Lower the thumb-covered end of the siphon tube into a bucket down below. Release your thumb and water will begin to siphon out of the tank. This makes a mess and you get both your hands/arms wet so it is not the most popular option but it works and you won't run the risk of sucking up water into your mouth. 

4. Partial Fill Method

This is one of the more difficult methods, it requires a larger diameter gravel vacuum attachment on one end of the siphon tube. Scoop water using your gravel vacuum, tilt the gravel vacuum upwards. Use your thumb on the opposite end of the tube to start/stop the flow of water. The water will drain out of the gravel vacuum, filling the tube when you release your thumb.  Stop the flow of water with your thumb before the gravel vacuum is drained completely which traps water inside the tube itself. Then place the vacuum back into the water slightly angled up allowing air to escape and the gravel vacuum to fill again. You should now have enough water into the tube to start the siphon once you release your thumb on the exit end. 

5. Mad Skills Method

This is basically a really quick version of the Partial Fill Method above in which you closely monitor the water level in your gravel vacuum and do it so quickly, you don't have to stop the water with your thumb in between the two scoops of water using your gravel vacuum. Somewhat hard to explain in words but once you get the hang of the partial fill method, it will become easier over time, and eventually, you can get it going pretty quickly with two quick movements.