Add some lilies for shade protection in the summer. And, what do you mean your bog is too deep? that just means more pea gravel is needed. LOL Add more plants to the bog, and assuming you have filtration running to the bottom of the bog, then up through the gravel, dumping back to the pond, that should help your green water issue greatly. My first pond turned green initially, but I've not had green ever since. I have, however, had murky water (last spring) and the koi pond takes longer to clear than the goldfish pond. Actually, the goldfish pond has been crystal clear since last summer! I'm a big bog fan, going to increase the size of bog in koi pond (hoping that will make that pond as clear as the goldfish pond ..) this summer. The goldfish pond has more invasive plants in it that grow really wild in the summer (water parsley, water clover, and penny wart to name a few) and totally cover the bog, thus filtering that pond more, plus it's about 1/3 the water surface of that pond. The koi pond's current bog is only maybe 1/6 of the water surface and the koi pond is deeper, so more water to filter.
The UV light may help. I say take a piece of your water line and your UV light to your local hardware store (Home Depot, Menards, etc.) and show them what you have and tell them what you want to do. They will tell you what you need to attach it "in-line". Then, keep enough of the line available (don't cut it off) so in the winter you can use a simple union to reattach the line, and bring the UV in. Then, get out there and show your hubby you can do it yourself! It's REALLY not that hard! The hardest part is convincing yourself you CAN do it, and making that cut.
