I had bio balls in Eheim ecco 2234 and had no problems mate they even came with the filter .buddah101 said:Can you please put up a picture of your Mag 350 with the bioballs in it? I would like to see it. I might do the same thing but would like to know if you have any luck using the bioballs totallt submerged? Although they are not designed to be used like that I would have to speculate that there is alot of surface area for the "good" bacteria to grow on so why not? Welp' lookin' forward to the picture.