its just stayin on the rock, and as apedroza said, its 'stretching' and moving to a different location. i have a single mj600 on my 30 which provides enough flow. the canister filter im using provides just as much flow as the mj. my gsp's and galaxia love it.

i do have sponge filters on both, but that was before i got the bta and never took em off.