It is not uncommon to see your betta hanging around near the filter. I have seen many bettas obsessed with the filter. Either they try to swim against the current or just hang around near the outlet of the filter. Why bettas are obsessed with filter?
Bettas like to hang around near the outlet of the filter because that spot has a good flow rate. A good flow rate means that spot has more oxygen than the rest of the tank. This makes breathing easier for the betta.
Bettas also like to swim against moderate current. This is one kind of entertainment for them. However, if the betta struggles to swim straight, that means the current is too strong for him and you need to do something immediately.
Is The Betta Struggling To Swim Near The Filter?
Look closely when the betta is swimming against the current of the filter outlet. Is it swimming straight? Is there any sign of struggle?
If you see the betta is struggling, then it is an indication that the filter flow rate is too strong. You need to reduce it immediately. That is not a problem with most modern filters as they come with an adjustment knob.
Just adjust the knob to your desired flow rate. However, if your filter doesn’t have an adjustment knob then what to do? Well, the best option will be to buy a better filter with adjustment knob.
But, if you don’t have the budget, there are some things you can do to tone down the flow rate significantly.
In the next section, I’ll talk about some of the DIY ways to reduce the filter flow rate.
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Reducing The Filter Flow Rate
Before discussing some of the DIY ways to reduce the filter flow rate, let me start by saying that the best way to reduce the flow rate is by using the adjustment knob. Most filters these days come with an adjustment knob.
If your filter doesn’t, chances are it is not a very good quality product and you might need to upgrade your filtration system.
With that being said, let’s look at some of the DIY ways to reduce the filter flow rate:
Use Pre-filter sponge

The first thing you can do is use a sponge on the inlet of the filter. Inlet is the opening of the filter inside the aquarium through which water enters the filter. If you can reduce the rate of water entering the filter, then it will automatically reduce the filter flow rate.
If you don’t have any sponge lying around, just take a piece of filter floss, cut it into a small rectangle and wrap it around the inlet. It will also act as a fantastic mechanical filtration.
Stuff Filter Floss Inside

If the filter flow rate is still too much, stuff some filter floss inside the filter chamber. Most HOBs have a divider inside their chamber. The divider divides the chamber into two compartments.
Water gets collected into the first chamber and then enters the second chamber through some kind of hole or notch at the top. At the second chamber, there are all types of filter media.
You can put some filter floss over the hole or notch through which water enters the second chamber from the first chamber. This second piece of filter floss will also create some kind of barrier in the water’s path and reduce the filter flow rate.
Create A Baffle
This is the best DIY method to reduce filter flow rate. However, it needs some working. You’ll need to have a plastic bottle first.
Cut the top and bottom of the bottle with a sharp scissor, also make sure the bottle length matches the length of the filter outlet.
Now, cut the bottle lengthwise so that it is no longer a tube. After that, you’ll need to attach the bottle to the filter outlet so that water first hits the side of the bottle and then falls down. The process is much easier to show than explain. If you are confused, just watch the above video.
This method will significantly reduce the filter flow rate. However, it doesn’t look good and may need frequent maintenance.
If you ask me, I’ll always recommend to buy a good filter that comes with adjustable flow rate options.