Sponge? on HOB wet/dry filter

[jerthunter]

I have a Millennium 3000 hang on the back wet/dry filter on my 65 gal tank. I have two questions.
1. Would it be a good idea to replace the black plastic bio filter with small pieces of LR? I have heard people have replaced bio balls with live rock pieces.
2. When cleaning my tank I noticed a lot of things growing on the plastic bio media of my filter, It appears spongelike to me. Just curious what it is.. I took the following picture of it, but it seems a bit blury to me, hope you can see it.

 

[jerthunter]

Anyone?
Is taking the bio filter media from my hang on the back filter out and replacing it with small pieces of rock a good idea? Better, worse, or no difference?

 

[acekjd83]

the rock (if its good, light, porous rock) will have more surface area than bioballs, but it is not designed to allow for water flow. water flow will probably decrease due to compaction of the rocks, whereas bioballs are designed to prevent compaction and to allow ample flow-through. in the end i guess its up to you, but imho, as long as you arent having any problems with it, you should leave it be...
its tough to tell what the "spongy stuff" is since the picture is blurry, but its probably accumulated detritus and algae with a healthy portion of bacteria. :notsure: