How to, and How Not to, Siphon Manually

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By Robert T. Ricketts, a.k.a. RTR


Every fish keeper needs to know how to siphon. This is one of the basic techniques in aquarium maintenance. It is second nature to everybody in the hobby, right? Maybe, maybe not. Do you get aquarium water in your mouth? Have you ever pulled the delivery end of the siphon out of the bucket and onto your shoes, the rug, or the hardwood floor? Maybe we should talk for a few minutes. I have done all the above, but eventually I learned how not to do so, and I'm more than willing to share what works for me. Think about it and see if anything here will work for you.

First, you need a siphon. These are commercially available at moderate cost. To have a siphon you really only absolutely require a length of flexible tubing just firm enough not to collapse when full of water and looped over the tank rim. About 1.3cm (0.5") ID (internal diameter) seems to be standard. Smaller diameter tubing would work more slowly in general, and clog more easily. Larger diameter tubing would work faster overall, but faster has as many disadvantages as advantages - floods and spills grow faster also.

Clear is better for me because I like to see what is going through and how fast it is moving. But we want a little more than that. We want a "gravel vacuum" on the business (in-tank, intake) end of the siphon. A gravel vacuum is a section of wider (commonly two inches in diameter) rigid tubing with an adapter coupling down to fit the 1.3cm (0.5") ID flexible tubing at the end. The length of the flexible tubing is not standardized, but for me should be at least eight feet. More on that point later. The rigid tubing that is most often original equipment is about 25.4cm (10") long. This is great for 10, 15, 20 long, 33 XL, tanks etc., all the ~12" high tanks.

It can be used readily in taller tanks as well, but if you wish, longer gravel vacuums are available. I have the standard 10", a 16" and what was originally a 24" gravel vacuum, and one now cut down to ~20". At one point I had one of the 30" tall tanks - big mistake, it was unworkable unless you like wet armpits. I do not (and I do have long arms). That tank went away, the gravel vacuum was cut to 20" and is fine for the 24-25" tanks, but for the smaller of those (30XH, 65), I'm more likely to use the 16" length for easier manipulation. For the big tanks (18-24 inches front to back), the extra length will be useful (but it will be more use with a Python attached than with a simple siphon).

Next you need a bucket, or if you can afford it (both money and storage space) 2-3 buckets. I prefer a Rubbermaid (USA brand name) (Roughneck is the type I have, food and water-safe in most colors). A pouring lip is very handy and for me needed, along with a sturdy bail (handle) - water is heavy. I like 11-19 Litres (3-5 US G.) buckets, but the latter are hefty if anywhere near full. So I use 5s, but fill to 11 Litres (3 US G.). I am clumsy. Internal volume calibration marks are good but not essential. These buckets absolutely must be reserved solely for fish tank use. Mark them in large letters on the outside, and if your cohabitants are not trustworthy, hide them (there is no small trick to concealing a stack of buckets). Soap or detergent residues can be deadly.

Siphon bucket1.jpg

Siphon and Bucket

You now have the basics. There may be other accessories that will make your life simpler, so I'll post a simple list of these:

Carpet protector strip

These are plastic mats, available from rolls, with relatively skid-resistant surfaces. They are intended to cover carpet along a walkway to be used by movers, workmen, etc. A length greater than your longest tank can be used during tank work (you are a workman here, right?) to protect rugs, carpets, and your relationship with your significant other.

Beach Towel

This is used to top the plastic strip (above) provided the resulting layers are still securely non-skid (test this before you start work, it matters). If not, spread the towel just beyond the strip, in the path toward the sink/toilet, to "walk off" any water on the soles of your shoes. I store the plastic strip loosely rolled inside a bucket, with the upper surface rolled to the outside to avoid dangerous curls when unrolled for use.

Folding or other utility chair

Have you ever been vacuuming away on the tank, trying to get that back corner, and run the bucket over? Or pulled the siphon out of the bucket without noticing? I've done both. Finally it got through to me that I cannot rely on myself to keep one eye on the bucket and hose delivery end, while the other is concentrating on the job inside the tank. I am neither a horse nor a chameleon. My eyes and brain don't work that way. I can slow down the siphon's rate of flow by placing the bucket on a folding chair. The rate of flow is directly related to the height differential between the tank water level and that in the bucket. That height differential is called the "head pressure" on the system. Raise the bucket, slow the flow. Lower the bucket, speed the flow. The chair seat height still provides sufficient vacuum for most cleaning purposes. It is especially useful when you want to control the suction for light surface skimming in planted tanks. I cheat even further - I place a hand or finger over the rim of the bucket, so I will feel the water when it gets to my fingertip. Bingo, time to stop vacuuming and change buckets.


Keep a plain utility towel around your neck, over your shoulder, wherever it is immediately at hand. Obvious, I hope.

Ready to Go

Okay, I've got siphon, towels, plastic strips, buckets and I'm ready to go. Turn off all submerse power to the tank. I use two plug strips per tank (both feeding from a ground fault circuit interrupter, GFCI, of course). One has the lights and their timers on it, while the other has the things I do not want live while I'm working - the filters, heaters, etc. While my hands are still dry, I flip the toggle on that strip. I have instant safety plus no sprays from exposed pumps or blown out heaters. The lights I leave on for working.

To start the siphon, position the receiver bucket where it will be ready, and feed the gravel vacuum end of the siphon into the tank, allowing the air to escape through the flexible tubing. Continue slowly feeding at least about four feet of the flexible tubing into the tank - or the whole tube if you are just developing the technique. The slow feed allows the tubing to fill with tank water. Using you thumb to seal the delivery end of the siphon, lift this end from the tank and to the bottom of the bucket. Release the delivery end of the siphon from your thumb and water should now flow freely into the bucket. You are siphoning, and you did not drink any tank water.

When it is time to change buckets, if you have multiples, stop the flow with your thumb, then move the delivery end of the hose to the next bucket. If you have but one bucket, stop the flow with your thumb again, then move the delivery end back into the tank. Make certain it will not flop out while you are away emptying the bucket. I usually lower the cover glass on it to secure the hose while I'm away, or just feed the whole tube back into the tank.

Finishing Off

When you have done as much vacuuming, removed as much water as you planned, just lift the intake end out of the tank and allow it to drain into the bucket. Pull the coil in the bucket straight up out of the water, allowing it to drain as well. This avoids slopping that last bit in the hose onto the furniture or the frowning spouse.

If you absolutely insist upon sucking on the hose to start it, the trick is to have a long hose (as suggested earlier). The gravel vacuum should be in the tank as before, at or near the bottom. The flexible hose is over the tank rim, drops to the floor, and is long enough for this scenario to reach from floor back up to the water level of the tank and preferably at least a foot above. If it does not reach that far, cheat by lifting the floor loop up enough to get the delivery end above the water level of the tank - a foot above is good. Now you may, if you must, suck quickly and briefly on the delivery end of the siphon. The water from the tank will be pulled over the rim of the tank and drop toward the floor. Once it is past the water level of the tank the siphon is technically established, but it is conservative to wait for it to pass the middle to the bottom of the tank before you remove your mouth from the tube - this is fast, watch and don't dawdle.

Once the water hits the floor level, cap the delivery end with you thumb. If you wish you can then lessen the pressure on your thumb and bleed out the air in the tube up to the water level of the tank. If you wait too long to cap the delivery end when establishing the siphon, the momentum of the moving water can carry it past the end of the tubing - i.e., you have a brief but messy fountain with no catch basin. By stopping it and then bleeding out the rest of the air, you have killed the momentum and most of the water spill or spray hazard. But the passive fill technique detailed before is much, much better. Tank water is not clean. Don't drink it.

  • If the delivery end of the siphon does not meet the bottom of the bucket and curl at least a bit there, your tube is too short. Take the rigid tube only (for a tight matching fit) to the local hardware store and get a longer tube. Do not get a connector or extension. Internal connectors can catch debris, plant leaves, etc. and lead to clogs.

Reproduced on the AquariumWiki by permission of Robert T. Ricketts, a.k.a. RTR