Custom Foam Aquarium Filters

AKA Hamburg Matten Filter

Custom Foam Aquarium Filter Sponge Filter ppi comparison

We will custom cut any of our foam sizes to meet your needs. You can make a full-tank filter, also known as a Hamburg Matten Filter in some circles. Whether you want a foam filter/tank divider, pre-filter for a sump, a piece to fit your own homemade filter or a replacement foam for another manufacturer's filter, we'll cut it for you as long as it's a rectangular piece. Our water-proof reticulated foam has much greater surface area than the Matala™ style filter sheets. There is no better filter material for nitrifying bacteria made anywhere! By the way, we don't force you to pay for full sheets where you end up throwing away the scrap.  Our foam is Made in the USA.  We've been using this exact foam in our own tanks for more than 30 years!  In fact, some of those original filters are still in use!

How to order: You have to select one of the stock sizes in the drop-down menu below.  That same exact stock-thickness of the stock size has to be entered into the "thickness" box of the calculator.  If you want a thickness that is less than an in-stock thickness, you must enter a quantity that divides evenly into that in-stock size.  For example -  If you want to order 1.5" thick pieces, you must order in quantities of 2, since we get two 1.5" thick pieces out of a in-stock 3" thick stock foam piece.  In the calculator below, the Maximum "Short-Side" we can cut on a custom-thick size is 12". If you order an in-stock thickness we can cut as large as 48" x 29".

Here's another example: If you want a piece that is 2.25" thick, then you must enter 3" in the calculator, since we do not have a stock size that 2.25" divides into evenly. Then, send a separate email asking us to cut it down to 2.25" (if the short side is less than 12"). 

If you want a 4.25" thick piece cut in half, we can give you two that are 2.125" thick as long as the short side is 12" or less.

Important Ordering Tips: When measuring for foam size, it is usually better to have it fit a bit tight. If the piece is too narrow, the gap will allow water to pass through unfiltered through the gap.  A piece that is slightly too large, will compress to fit the space and will work exactly the same.  It also stays in place better.  We recommend adding at least 1/4"  to the length or width for every 12" of foam, on any side where the foam has to fit tightly between two walls. We are unable to be perfect on foam cuts.  We will be accurate to within +/-  1/8" on all cuts. If you need to cut a bit off a piece, a very sharp knife guided by a straight-edge works well.

Custom-Cut Foam

Thickness:  (Inches)

Long-Side: (Inches)

Short-Side: (Inches)

Price Ea. : 

Quantity required:   


  • Select PPI/In-Stock Thickness from Drop-down Box. If it's not in this box, it's not in stock.
  • Enter the exact size you want cut to the nearest quarter-inch (¼ as .25, ½ as .5, ¾ as .75).  Custom-thick pieces have to be ordered in a quantity that divides equally into the in-stock thickness.
  • Enter the quantity needed of that size you just entered into the calculator
  • Click  ADD TO CART

Maximum Long-Side is 48""
Maximum Short-Side is 29"

Keep in mind that it doesn't matter what we call the dimensions. The maximum long side is 48" and the maximum short side is 29".  You can position the long side any way you want in your aquarium.

You are ordering only foam. Nothing else comes with the foam for using it as a filter.

The shopping cart  will not figure the shipping correctly on some orders, especially if you choose anything other than "Ground" or if it's a very large size.  The carriers charge dimensional weights on some large, light-weight packages and it can greatly affect the price. The cart cannot be programmed to take this into account.  If the shipping is not correctly figured by the cart, we will let you know before cutting your foam, so you have the opportunity to cancel if you want. 

Note:  The foam pieces may have to be folded or rolled into a smaller package.  This is done to save on shipping charges (sometimes the savings is significant).  If you want your piece to remain flat during shipping, let us know and we will inform you of any additional shipping charges that you may have to pay (carriers charge a dimensional weight, which applies to large, light-weight packages).   When receiving folded or compacted pieces, just place them on a flat surface and within a day or two they will regain their original shape.

If you do not see a box with Tabs below it means your display is too small for this feature to work. For this additional information you should view this on a device with a larger display.
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Many of these Hamburg Mattenfilter style filters have such a large surface area that they out-filter much more elaborate and expensive filters on the market. Maintenance is simple and there is almost nothing to ever break or wear out.

PPI - stands for pores per inch. So, 50 ppi means 50 pores per inch, which means they are smaller pores than 15 ppi, which is only 15 pores per inch.

Smaller pores tend to clog quicker, but offer more surface area. Literally all pores sizes will over-filter a heavily stocked aquarium. The biggest considerations are usually how quickly it will clog or are there any new-born fry that may swim into a large pore size.

General Miminum Thickness Guideline for Tank-Dividers that will stand on their own:

  • 1.5" - no more than 10" wide
  •    2" - no more than 15" wide
  • 2.5" - no more than 18" wide
  •    3" - no more than 24" wide

Shipping Quotes

The shopping cart will enable you to get a shipping quote before paying for an order. Simply add the items to the cart, view the cart by clicking on the "view cart" link in the upper left corner and it will enable you to get a total for the shipping before committing to an item.

Learn more about this product in these articles.

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Put it in as a second stage in my multi-media filter unit and couldn't be happier.
Mark Hanson, Wed Dec 20, 2017
After 4 months use, I can only wonder why I didn't switch to these years ago. Maintenance is almost nil.
Jeremy Chadwick, Thu Aug 20, 2015
I love these wholetank filters. Slide it over and you have a divider!
Joe Orosz, Mon Aug 25, 2014
I can't believe how many fish I'm able to keep in a tank with one of these as a divider/filter. Best bio filter on the market.
Pete Harris, Tue Aug 12, 2014
I've switched all my tanks to these because I've read that some major breeding operations are using these without ever cleaning them, and produce fantastic fish from those tanks. So far, I couldn't be happier.
J Wojcik, Wed Mar 19, 2014
I've been using your foam filters for decades and they're the best. Since this is the same great foam, I'm sure my HMF's will now also be the best. Thanks for a great product.
Bill Howard, Thu Feb 20, 2014
In love with this foam! I thought I wouldn't like the look of it as a HMF style but instead I now prefer it. I am using my powerheads instead of lift tubes with great success. I'm buying more right now. PS great fry food sample also!
Val Crismore, Tue Dec 03, 2013
My custom foam filters arrived promptly and they fit perfectly. The free food sample was quite generous, too!
Mark Fisher, Fri Aug 02, 2013
I tried making one of these and it was pretty easy. Filtration is great, but I wish it wasn't so obvious in the tank. It is a good idea for a breeding tank but it stands out too much for my decorated one.
Alice Cabisca, Mon Jul 29, 2013