Dual density filter cartridge

Abstract

The invention relates to aquarium filters providing improved water filtration without accelerated clogging. The present invention also relates to methods of using such filters.

1 . A water filter article, comprising: 
 a.) a first porous filter wall for filtering liquid flowing into the filter article; and    b.) a second porous filter wall for filtering liquid flowing out of the filter article    wherein the density or surface area of the first porous filter wall is less than the density or surface area of the second porous filter wall.    
   
   
       2 . A filter article according to  claim 1 , wherein first and second filter walls are comprised of a water permeable filter membrane material.  
   
   
       3 . A filter article according to  claim 2 , wherein the filter membrane material is selected from the group consisting of nonwoven fabric material, polymeric foam material and mixtures thereof.  
   
   
       4 . A filter article according to  claim 3 , wherein the filter wall comprises a nonwoven fabric material.  
   
   
       5 . A filter article according to  claim 4 , wherein the nonwoven fabric has a fabric weight per unit length ranging from about 2 to about 15 oz per linear yard.  
   
   
       6 . A filter article according to  claim 5 , wherein the nonwoven fabric material of the first filter wall comprises a blend of fiber deniers ranging from about 4 to about 20 denier.  
   
   
       7 . A filter article according to  claim 5 , wherein the nonwoven fabric material of the second filter wall comprises a blend of fiber deniers ranging from about 1 to about 8 denier.  
   
   
       8 . A filter article according to  claim 3 , wherein the filter wall comprises a polymeric foam material.  
   
   
       9 . A filter article according to  claim 8  wherein the polymeric foam material of the first filter wall has a density of from about 10 to about 25 ppi.  
   
   
       10 . A filter article according to  claim 8  wherein the polymeric foam material of the second filter wall has a density of from about 20 to about 45 ppi.  
   
   
       11 . A water filter article, comprising: 
 a.) a first porous filter wall for filtering liquid flowing into the filter article;    b.) a second porous filter wall for filtering liquid flowing out of the filter article; and    c.) a frame positioned between the first and second porous filter walls for providing structure to the filter    wherein the density or surface area of the first porous filter wall is less than the density or surface area of the second porous filter wall.    
   
   
       12 . An aquarium water filter article, comprising: 
 a.) a first porous filter wall for filtering liquid flowing into the filter article;    b.) a second porous filter wall for filtering liquid flowing out of the filter article; and    c.) a frame positioned between the first and second porous filter walls for providing structure to the aquarium filter    wherein the density or surface area of the first porous filter wall is less than the density or surface area of the second porous filter wall.    
   
   
       13 . A method of filtering aquarium water, comprising the step of filtering aquarium water through the filter of  claim 1.