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Filter Currents: A Betta's Worst Nightmare

Filter Currents: A Betta's Worst Nightmare

Many people need some way to slow down the current of a filter, whether because their fish are being thrown around in it or because their betta, a species notorious for their hatred of water currents, despised it. I have had the same problem, and designed a system to help alleviate it.

Stopping the spectre

The vast majority of filters sold in the US are of the Hang-on-Back type. These typically have a 'waterfall-outlet,' where the water falls down out of the filter into the tank. The obvious problem is that as the water falls from the outlet, it accelerates under the force of gravity until it reaches the waterline, then creating a strong current.

The secret to stopping the current is to simply obstruct it. The most efficient way to do this is to use the body of a half-liter soda bottle. I will now describe how to construct the device.

Step 1: Start the incision...

You must first cut the soda bottle appropriately to prepare it for mounting. On the right, you will see a diagram for the first cuts, labelled "Cut 1." You must remove the two ends of the bottle, leaving only a smooth cylinder from the center of the bottle. Next, you need to tear off the label and cut the cylinder along its length, right next to the strip of glue, as shown in diagram "Cut2." You should now have a simple sheet of curled-up plastic.

Step 2: Duct Tape and BubbleGum

This step is very simple: simply tape one end of your plastic sheet - the end with the glue on it - to the top of the filter, and bring the other end around under the outflow, as pictured at left. (I outlined the edge of the sheet so you can tell where it goes) Then you're done, go play in traffic or something.

© Eric Smith,
If you have any suggestions for this page, please send them to I wish to make this page as clear and understandable as possible, and your input would be greatly appreciated.
Name: Joe
Comments: Great system! I tried this out on my ten gallon tank and it works perfectly. I set it up so the water streams are deflected out the sides of the plastic. Amazingly simple, yet it works.

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Comment : I recently got a male betta and one and bought the Hawkeye Aquawview 360 2 gallon kit. The filter part has a cylinder in the middle. My betta got down in there. Scared me to death. Is this a problem and dangerous? Please help, my first fish and it is my step daughters. Thanks, DD
Posted by ddschaech on 2009-04-25
Comment : Great! broke up the current perfectly and has made my betta much happier in his new home a 20 gallon long oak tank.
Posted by Santaaa on 2008-12-23
Comment : Thank you Thank you Thank you! Frank is sooo much happier! oww, i was gettin so worried there too. :)
Posted by Lizz and Frank (Betta) on 2008-10-04
Comment : This is very helpful, thanks! I was ready to do this until I realized that my filter is open (at the top you see the water flowing around the cartridge, but nothing over it) but I'll figure something out. My Betta will appreciate this.
Posted by Dominique on 2008-10-01
Comment : Brilliant. Me and my dad are both fish nerds, and when I showed him this he was quite impressed :-)
Posted by Eric on 2008-05-01
Comment : brilliant! i was prepared to go a buy a submerged filter, but this is much better thanks!
Posted by Brandy on 2007-11-07
Comment : I am relieved to find a way to slow down the flow of HOB filter. For even thought my betta doesn't mind it the filter messing up the sand substrate.
Posted by Dawn on 2007-10-28
Comment : Wow. This is so practical and easy. My betta Spunky just got a new tank (VERY EXPENSIVE!!) and then I noticed that everytime I turned the filter onn he ran off to a corner and would not move. I noticed an online artical saying tat betta's HATE strong currents. In a frenzy, I found this artical, made the device and now I have a very happy fish. (and a less worried owner) this was great!! It helped me SOO much! Thanks!!!!
Posted by Jessica on 2007-05-06
Comment : Perfect! And simple, as most perfect things usually are. Thank you so much!
Posted by Susan on 2006-09-17
Comment : Fantastic! I was on here shopping around for a new "quieter" filter. Low and behold, I find a solution as simple as this! Thank-you Eric!
Posted by Robin on 2006-09-17
Comment : Amazing!! I used it on my Whisper filter in a three gallon tank. I thank you, Floyd (my Betta) thanks you, and my pocket book thanks you (I was going to have to buy a new, "adjustable flow" filter to keep the little guy from getting bashed about)! Isn't it silly that sometimes the solution can be so simple? I wanted to smack my forehead (Doh!!).
Posted by Sara on 2006-07-15

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