Help with filter

[bangkokbandit]

My tank has a built in filter.
At the moment it just has a sponge pad at top followed by plastic bio balls.
I will add some ceramic bio media.
Should i add this around the pump at the bottom, or in the section with the plastic bio balls but just under them?

Also there is a lot of brown algae growing on the glass in there, is this a problem or should i just let it be?

Thanks

 

[ScaryFatKidGT]

Throw out the plastic balls and put in matrix or biohome, abut a billion tomes more surface area than plastic

 

[bangkokbandit]

Thanks for reply. I will do that once i get enough media.