So The sponge in my AC
20 was getting simply nasty, and was impossible to keep clean. It was literally brown... Permanently. My trate were steady at 20ppm but my phosphates were REAL high. Started to get some green hair algae.
I had a spare laying around so I switched it out with a fresh purigen.
I have heard that the sponge (8 months old in my case) can hold tons of BB. Is this true? will changing it affect my tank? I am also running biomax the filter.