Mike is right on the bead filter needing cleaning, but that is true of any filter. The up flow bogs are notorious, because people are told that they don't need any maintenance, but take one apart that hasn't had maintenance and see what you have. As for bead, I have used three different varieties of the upflow, what I will call true bead filters, one being the SacKoi 15 like Powerman. They do a super job with fines, because the beads fit together rather closely, and the longer it goes between cleanings the more efficient it gets due to clogging of the pores, and this causes the flow to fall off noticeably. The biggest difference in the two is price. I have my filters inside a yard shed near the pond and don't have to hide the barrels that would be feeding my waterfall.
As for statements that the bead filter is primarily bio and not for fines, or primarily fines and not for bio, mine do both jobs and do them well, but the 4000 gallon pond has two bead filters that are rated at filtering 19000 gallons of ponds. One word of caution with enclosed filters, if the power goes out, oxygen levels will deplete rapidly by the bio bacteria that form on all surfaces exposed to water, and will go anaerobic, creating hydrogen sulfide gas pretty quickly, so they need to be backwashed on restart.
If you get a true bead filter, you want one with a blower to shake the beads to get them clean. Some of the early models were made without the blower, then they were offered with optional at additional cost blower units. Now I am not sure of the availability of the old no blower models.
Zone 7 A/B
Keep your words sweet. You never know when you may have to eat them.
Richard