I have phosphates in my tap, but not as high as yours. Runs about 1ppm or so. I started out using the chemical medias to keep them down, but eventually gave up on that. I have no idea what level my tank phosphates are now, and I have a couple dozen tanganyikan species in a number of tanks that don't seem to be affected at all by the phosphates. Some say it promotes algae, but I use nerite snails, so I don't care about that either. My oldest tang setup is four years old now. All the others I've had for over a year. I'm not sure if there have been any studies done, but that's been my experience. It'd be really impractical for me now to worry about phosphates in what are 20+ tanks, some with sponge fitration only. My experience has not proven the need, but again, your levels are higher. I'd be looking at a whole house filtration system, which may not be a bad idea anyway to ensure other possible toxins aren't present in the water. I really don't think phosphates are our fish's worst enemy. Maybe I'm being naive, but unitl I have a problem, I'm not feeling motivated to add the water purification equipment.
If I were you, I'd be googling and looking for studies done. If you can't find any, then I'd try to run with things as is. Don't just go by the "phosphates are harmful to fish" advice that you'll see out there on various websites. Here's an article in the forum library
and the only detriment mentioned is the promotion of algae.