There's a simple solution if you can do a little plumbing. UV definitely work better the longer the water is exposed to the light and the same basic principle is for filters the slower the water flows through the less debris is forced through the media. With that if you split the supply line before it gets to either the filter or uv creating a by pass add a couple ball valves to regulate how much flow goes through your filters. Just connect the bypass as the water comes out of the filters " You can keep the wanted gph to your falls and not max out your filters yes some water will not get filtered but if your system was doing ok at lesser gph then the only change should be your o2 levels which should help your over all pond health.