The light faded away on Friday, so stopped for the day. Washed the gravel as best I could to remove a good amount of roots.
After lots of washing gravel, it was finally full. Still have room to add some more gravel later. Finally got around to adding a union, so winterizing will just be a twist and the hose is removed. I'll modify a clean-out lid in the future, so I can flush it with a garden hose if needed. But it does siphon the opposite way when turned off, which may help in dislodging debris.
I returned some of the plants, keeping the grass out, since they were really rooted to the bottom and very hard to get out without removing the gravel almost to the bottom. Hopefully as they root a little, they'll be more upright.
A view from the front, flowing into the pond. Hopefully with some root maintenance, it will last longer without having to dig out the gravel. It definitely works great either way, filtering it crystal clear in a short time period and haven't had green water since installing it. I was constantly fighting green water before with the submersible filter.