Can anyone help im having a nightmare with my filter
 

HI there, I have a 560 gallon pond with a bio force 9000 filter. I have 2 koi, goldfish and orfe. My filter keeps blocking and have to clean pads every few days. I was told the filter was not big enough but looking at the stats on it seems ok. I also have a yamitsu pre filter on the pump. The pad in that keeps blocking up too. Also have filter wool in the bottom of the bioforce filter. Anyone any ideas without buying a new filter what I can do? Was looking at taking the bio rings out of the bioforce filter and putting them in the Yamitsu filter then replacing the ring in there with alphagrog lava rock as that seems good for biological filtering. Is this OK or had anyone any better ideas.

Thanks