# Fixing the Fluval 204/304 bypass problem



## cgmark (Aug 18, 2010)

I like the fluval filters but the 204/304 series has a bypass problem. The problem is the lid when attached leaves about a 1/4" space between the intake for the pump that returns water to the tank and the filter basket. What happens is water enters on the opposite side , fills the canister and some of it then goes right back out the outlet bypassing the filter completely. It might seem like 1/4" space is no big deal but realize that is spread over an area of the entire intake and it adds up to the equivalent of a 1" pipe worth of water being bypassed.

Some people have pulled up the foam pads to bend them over in an attempt to block the bypass, but that doesn't always work and still bypasses the rest of the filter baskets.

A quick solution is to fill that space between the pump and the filter basket. The easiest for me was foam rubber. Foam rubber is sold in school supplies and is non toxic. It is about 1/4" thick . Using scissors cut a piece slightly larger than the outlet of the filter box top. Then trim out the center so you end up with a round ring of about 1/2" wide rubber. What you are doing is basically making a very soft washer.

Then just set it on top of the outlet and gently lower on the top and press down. You can tell if you got it right because it takes a little more pressure than usual to push it down.

With the washer in place the water has no option but to enter , flow through the filter boxes and out the outlet into the pump.

One downside and why I think they did what they did with the filter, air. Getting the air out of the filter after you clean it out is a bit more time consuming than without the washer. Before the washer the air entered, got sucked up by the pump and exited. Now it gets trapped in the top and the only way out is through the filter boxes. Basically it involves tilting and tapping the filter till the air is pushed by the water through the filter. It takes a few minutes but once its out that is the only downside I have found.

I waited on posting this because I did this to the filter 2 months ago and wanted to test it out for any problems. The difference is big. Before the filter would have some debris in it but less than expected. Now it is filled with all kinds of gunk when I clean it.

I paid $1 for the foam at the dollar store. 
This is what the foam looks like
http://www.joann.com/joann/catalog/prod ... D=prd28413


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## toledo guy (Jun 23, 2010)

Thanks for the tip. I have a fluval 405 and have lots of debris present in my 75g. So I tried your project out. I searched all over the house and garage for some kind of foam to use. None! Then noticed a new box of Magic Erasers. They are foam but denser than what you used. I cut one in half, then pushed the top of media cover into foam to outline the opening needed. I cut the hole with a filet knife. I also had to thin the foam slightly. Cover went back on fine just took a little extra pressure. Now after two hours of running my tank is free of debris. Now can't wait to see the things that were bypassing the media.


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## KiDD (Aug 20, 2010)

You might want to make sure the Magic Eraser does not have any kind of chemicul in it. I think it has some kind of cleaning agent in it.


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## toledo guy (Jun 23, 2010)

I have checked out the Magic Erasers thoroughly. Seems they are made of melamine which is a plastic. There are no chemicals in them. Though by time i open can again i will have the type foam you describe.


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