I actually did the Triton test to see if anything bad showed up, the only red flag was copper but this was well under the natural ocean levels for copper. I ran polyfilter for a while to be sure.
I use a seneye so PH and Ammonia are constantly monitored. I bought a brand new KH test kit so know its at the right value.
I dont have a sump, my setup is very simple, I have the main tank, hang on side skimmer and hang on side GFO reactor. I just remembered though that there is something in my tank, a small piece of a 'Juwel' tank lid. Basically I cut a section out of the lid for my skimmer piping and was using the cut off piece to stop water going through a cable hole behind the tank, but one day it fell in and landed right at the back. I figured it was material used for the tank lid so shouldn't cause a problem, maybe now i'lll fish it out!