Sunfish with Slider Turtles

Lepomis, either L. punctatus or L. marginatus, I think, in my 120-gallon home aquarium. October 17, 2015.

Over the years I've tried to find fish compatible with Trachemys scripta (sliders). Early attempts included Ancistrus dolichopterus (bushy-nose pleco) and Chromobotia macracanthus (clown loach). Unfortunately, the loach was harassed relentlessly by the turtles and under a lot of stress. I was afraid it might be devoured and decided to pull both fish from the tank, although the pleco was never bothered. The loach probably appeared to similar to the goldfish which I regularly fed to my turtles. Had it been larger and more mature, things may have been different.
Interestingly, two of my feeder goldfish did survive the first couple days with the turtles and went on to live happily in the tank for several months. Eventually, they grew large and got messy so I put them in a backward pond where they were promptly devoured by the local racoons.
I also tried Tanichthys albonubes (white cloud mountain minnows). These worked very well. I had a pile of rocks in the tank were the fish could retreat to and breed. The old and sick were picked off by the turtles (usually my Graptemys pseudogeographica) but the fish bred quite often, replenishing the population. I only rarely had to buy new fish. They were pretty little fish with white and red spots and stripes. However, I eventually stopped buying new fish and hand fed the last survivors to the turtles.

Trachemys scripta elegans, in my 120-gallon home aquarium. October 17, 2015.

I've always had an obsession for things that were "natural." It always secretly bothered me that the minnows were not native to the same rivers as the turtles. The fish were from China, the turtles from the United States. Once I moved to Florida, I decided to try some native fish with the turtles. I introduced two, then one more, Lepomis (sunfish) to the tank. They were all between 2-4cm in length. The turtles were outside enjoying the sunshine when I introduced the fish, so they could become comfortable before I returned the turtles. Hopefully, the turtles wouldn't see the new addition to the tank as food if it was already there when they arrived.
It worked like a charm. The turtles were a little curious at first and took a couple nips at the fish, but the fish were too fast and the turtles lost interest. They lived with the turtles for several weeks and I fed them bloodworms once a day, with the turtles regular feeding of krill.
Unfortunately, I had vacation plans in Canada over Christmas break and I left my little indoor community with a sitter. I also added a school of Gambusia holbrooki (mosquitofish) and another sunfish about a week before I left, but they seemed to settle in tolerably, with the exception of the disappearance of one of the mosquitofish. When I returned, all but one of the sunfish had disappeared. Just a couple days later, it too was gone.
I'm not sure exactly what went wrong. It might have been the hanging planter I installed as an egg-laying box for my female slider. Or it might have been an increase in bacteria or ammonia and nitrates. I wasn't here, so I don't know how the fish died. I'm thinking I'll try the whole thing again at some point, but maybe I'll just wait until the summer, when I'll, presumably, be at home more often.