My bottom drain aerator has been bubbling funny for a while. The dome finally came undone today.
Let me call that XXXXX contractor.
Wait, I had no contractor I installed it myself.
Since I can't blame anyone for this, time to lower the water level and fix the problem. First challenge, walking on slim coated koi pond bottom. So I slid all the way to the bottom drain. Before I can screw the dome back on, I realized that there were rocks and other junk in the bowl. The water level was still too high for me to easily clean the bowl. Time to water ballet back to dry land and pump out more water. Repeated the same drill one more time and finally got everything fix. The only thing fortunate about the whole ordeal was that the dome came loose at the thread so re-installing it wasn't a big deal.
Now I get to enjoy my "like new" aerator.