I dont have your answers but do have a few observations. If you have not
changed your uv bulb that could be part of the problem. If a bigger pump
will 'blow out all the poop', wouldnt that mean it wont catch it in the
future? The LFS is in the business of selling equipment. If you tell them
it's broke it seems reasonable they are going to tell you to fix it with
bigger, better equipment from them. This may not be the case but possibly
you are going to have to deal with 'a mess' to restore the previously
working system to its successful status. If you upsize your pump it does
make some sense that your filter could inadequate for a sustained higher
flow.
Bill Brister - Austin, Texas