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Water Flow Question

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  • Regular Member

Few days ago I installed a new Fluval output nozzle because I thought it would be nice to change the water flow to something that’s less strong and more evenly distributed.  I swapped out the standard nozzle that has a really strong single direction flow.   The new nozzle has 2 ball areas that open up to these big flow directors (photo attached). I’ve got one nozzle pointed up toward the surface So it is still moving. The second is pointing downward toward the bottom of the tank to keep the water down low moving.

Should I be worried that I’m not getting enough water movement around the tank to get good filtration flow? I’m using the full flow rate for this Fluval 406. It’s been four days since I put it in, the fish seem to be relaxed with a less harsh flow, but I’m also seeing a lot of waste sitting at the bottom of the tank around the plants. 

Any advice Would be appreciated.





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  • Regular Member

Hey, I know this is an old thread but the fluval 406 is a pretty substantial filter.  


You should be fine as long as theres lots of surface agitation on the water in your tank. 

If those fancy nozzles help then great but , I sorta doubt trying to upgrade the output nozzles on a fluval 406 is going to make a huge difference.  But, from what I can see in your pictures, you couldn't have effected the functionality of the aquarium in any meaningful way.   It may even have helped it.


If in doubt, aim both of those nozzles upwards to increase surface agitation to help aid with the off-gassing of nitrogen that occurs during the nitrogen cycle process. 

But,  your config with one nozzle up and one down could also be optimal because you can cause surface agitation while also causing water circulation within the tank.  So, with that said just go with what you feel what works best.  


If the fish are gasping for air at the top of the tank it may mean theres insufficient water circulation and/or water surface agitation.

Edited by Goldfishbeginner
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