Random Bits of Projects

March 8, 2009

Convert an old-style filter cartridge for the new Tetra model. Save money and customize!


(Finally a post!! Woohoo! Geez, long title huh?)filter-cage-new-filter

Some of you out there may be thinking of getting, or have bought, a the newer version of the Tetra, Whisper filter for your fish tank. The type that hangs over the back. The price of the filter cartridges that go with these new ones are expensive when compared to the old models that you can buy in bulk and assemble yourself. This might be putting you off. Or you have several old cartridges laying about you need to use up. Or you maybe your store does not carry the replacements (recently here). Well there is a solution! (Insert happy noises here!)

I have had their old version of Whisper filters for years. I generally like them for the price range. I have tried a handful of other brands that are either loud or do a lousy job, when compared to this one. These last for years, usually are quiet(ish), do what they need to do, and are easy for customizing the media you use, among other things. These also come with extension tubes, unlike one that is similar to these being sold. A few months ago I had to send my husband to get a new filter to replace one that finally conked out of many years of hard use and neglect. He came back with this new model. Yikes! It was all they had.

I have two now as of this posting and they work well (no they do not, as of 2011). I am not as wild about the insert for bacteria colonies as I am the old version, but otherwise I cannot complain (I do now). One is very quiet, the other is not so I cannot really say there. The one that is noisy came in an opened box so I am guessing the quiet one is the normal mode.

But I did get the nasty surprise on how much the filter cartridges cost. They work very well but I can build my own to be comparable and less expensive. So of course, I had to dabble.

Hopefully the following will give people options for filter cartridges for a filter I do like. I hope the pictures do not move around like some previous posts.

Converting an old style filter to fit the new filter cage:large-filter-and-box1


  • scissors
  • Large or regular size cartridges, not pre-assembled. Whisper brand (in picture)  and one other brand I forgot. The skeleton comes in blue (here), black, and maybe green that I have seen.
  • Filter media (comes with carbon), Ammo-chips type media optional.
  • New Tetra, Whisper Filter (EX 30 shown in this post)

The new system has a cage that holds the filter inside. The old style has a “skeleton” that slips inside of the filter with the media to keep it rigid. The goal here is to modify that skeleton to fit within the cage. Slipping the old style filter inside without it does not work well.

filter-cages-side-by-sideYou will see the bottom of the old type has corners where the cage is curved. The top of the cage also is angled where there are corners at the top of the skeleton (hard to see in this picture). We will cut these corners out.

There are many spots you can cut. The one shown here is not my favorite but I did not want to pull out every filter to find the one I like better.

1. Cut in the middle between the inner rungs. Then cut between the outside edges and the rungs. I cut off the corners completely here but this can snag the filter when you are inserting it. So you may want to leave the corners on and just trim off excess plastic that gets in the way. There is not a perfect way to do this so mess around with it until you are happy.

filter-skeleton-cut2. Next, cut the top corners at an angle. I start my angle where the flaps connect together at the top. Again, there is plenty of room for error. You just need to be sure you can still close the flaps over the filter when you are done. There is a close-up view of this in the picture below the one to the left. Notice the angled corners of the skeleton you cut.

3. Now slip the skeleton inside the filter floss pocket. You may need to put your hand around the cut portions while you do this. Your hand should fit. Sometimes the cut portions snag (like the sides of the one shown in the picture…grrr).

4. Now add the carbon that comes with the filter cartridge and any other media you like adding. Ammo-chips in this case (gold fish tank).

top-of-filter-in-open-cage5. Fold the  top, plastic flaps over the top and clip in the middle like normal.

6. Open the cage of the new filter and slip the cartridge inside. The top should not prevent the cage from closing. Trim more if it does.

You will need to fold the bottom of the skeleton towards the center to fit inside the curve of the cage.

7. Fold the corners, that no longer have the rigid skeleton inside, towards the back of the cage. (Yes the one here is dirty. I did not want to wait to post this until I had to replace the filter.)

filter-corner-tuck8. Close the cage. You may have to poke some of the filter inside but it should filter-cage-sidefinally fit just fine. The picture to the right shows a loaded cage from the side. This one has been used so it is a little wet and saggy.


You can reuse the skeleton so you do not have to trim a new one every time you change the filter.

I have been using this method for several months and I am happy with it.

Sorry that the pictures do not align perfectly with the text. I have problems getting pictures to stay where I want them so I am not going to get too picky. 😦

filter-loaded-back This (left) is the back view of a finished cartridge. This one is in use so it is dirty. Bleh. Notice the corners sticking out. This is fine. They fold up when you insert the filter into the main unit (right).inserting-filter The thing in front of the filter is for bacteria to grow on. It is OK. I like the sponge better. My opinion. 🙂

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  1. Hi Amy!

    I just bought one of these new Tetra Whisper EX45 filters and did so only because I had over a dozen of the old Whisper filters that were unused. I have a jerry-rigged version in my tank now and really appreciate your tutorial here. Way to go!

    Thanks, again!


    Comment by ShawnXian — April 19, 2009 @ 7:50 pm | Reply

    • Great! I was not sure if this would be useful to anyone but figured I would throw it up here. I am thrilled it works for you! I hate being stuck with only one option for filters like they were doing there. 🙂

      Comment by virtuallyamy — April 19, 2009 @ 10:04 pm | Reply

  2. Thanks so much for posting this. I have 4 aquariums, three with the old Whisper filters. The old 2-cartridge whisper on my 55 gallon died recently and I bought this new one not realizing the cartridges were different. I buy the bio-bags in bulk through Big Als and have a ton of them left so I’m happy I’ll be able to use them. Plus, I think the prices on the new cartridges are outrageous. If I can get this to work I will continue to buy the bio bags. With my old Whisper filter, I rinsed off the bio-bags each week when I cleaned the tanks and they were always filthy. I’m not seeing that with this new filter so I’m also concerned these new filters are not working as well. Have you noticed anything like that?

    Comment by Susan — April 25, 2010 @ 7:27 pm | Reply

    • HI! Glad this helped! I continue to convert these filters, it has worked very well. Saves. Also allows you to customize what you put in them. Thanks for letting me know!
      I keep meaning to update my opinion about the new style. When I wrote the post, I have not had them that long. Now that I have, I cannot say I am impressed. They are harder or more annoying to clean and I have had them get quirky on me more often than the old style-details later. I also hose off my filters like you mentioned. I find they generally get as dirty or at least close to the same (29 and 55 gallon tanks combined with old filters) but I still do not like them as well. I will update and babble in length about it later. I will mention what you said too. 🙂
      Turn the intake so it is less flush with the wall. That helped a bit as I think I remember having a similar problem as you earlier on. The plastic thing for bacteria to grow on does not seem to do as well either. You may need to prop the filter so it is tipped more towards the tank. I get better flow.
      So to make the long version shorter, I think they do not perform as well as the old style when I take into account the maintenance and dealing with issues. I have also already had one die on me where the others have lasted years. I was happy when they kept it simple and they worked. Why change it? Oh well. At least we can convert the filters and not get stuck with the others. And these do work much better than a few other brands I have tried. Not saying much considering how bad a few of them worked.

      Comment by virtuallyamy — April 25, 2010 @ 10:09 pm | Reply

  3. […] the Tetra, Whisper Filter systems for 2 years (already?)  now. Size EX 30 and 45. When I posted on how to convert the filters to something less expensive and customizable, a reader had asked if I noticed a difference in their […]

    Pingback by Review of Tetra, Whisper Filter (EX 30, 45) « Random Bits of Projects — January 16, 2011 @ 12:53 pm | Reply

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