I did this for a couple years even with a skimmer and my nitrate test showed 10-60 nitrates. I bought a new kit and it registered 180ppm!
No wonder my clams didn't survive and I was starting to lose some corals! I had a fuge but couldn't even keep macro algae alive toward the end!
It was amazing anything pulled through.
This was a very very established system.
I've since tripled my skimming capacity and do at least monthly large water changes (45 gallons on a 180+ 55 fuge)
Important to also note that I overstock my tanks. Probably even more now.
I am able to keep many more difficult fish than I used to though haha!