Filter sponge needs changing??

[Sarkis]

i have had my tank up and running for about 4months now. I do weekly water changes. I read a post the other day it said take your filter out ( the sponge part ) and clean it in a bucket of tank water. I did that, when i took the sponge out to clean it the back side is so badly coated with Algee and other dirt that i cant clean any of it off. I mean there is probably a 1/4inch of grime on the thing. Can i go buy a new one or is that going to hurt the tank. BTW its a top fin 40. I also have a penguin 125 on my other tank which is in the same state. Any help would be great

 

[The-Wolf]

when adding new sponges, first rinse the old in a bucket of tank water. Then immerse the new sponges in that dirty water and squeeze them.
You now have transfered some bacteria to the new sponges.
Yes this make them slightly dirty but that is the point.

 

[WILDER]

You can also cut the new sponge in half and just replace half, removing half of the old sponge.

 

[Sarkis]

You can also cut the new sponge in half and just replace half, removing half of the old sponge.

i'm sorry i wasnt to clear, but they are the drop in cartridge type filter. Im not sure if i can cut those