I get my tilapia from whole foods and I trust their process, the taste and quality is also vastly different this is the only place I would get tilapia from. If I did not have whole foods I would get something that was 100% fresh caught and not farm raised that was a lean white fish. For me (dont want to speak for others) I added fish in when I did because I was tired of eating chicken 4-5x per day and it added another source of protein for me that I enjoy. Its also very light and causes zero bloat for me, these are the reasons I am eating it. If you actually look at the nutritional value tilapia has more fat than trimmed chicken breast so this is not my reasoning for doing so.
As far as rice goes I use it again due to how well it digests for me and that there is water in it, this is also why I choose to use it because I am going to load on it so I might as well use sources that I am going to use at the end. I do use oats and potato with a good bit of my athletes but 99% of the time toward the end I transfer them to rice, fiber with reduced water is where a lot of the bloat you see on stage comes from in my opinion or just overall food volume being too high without enough time and fluid to digest it. Ive yet to see someone bloat from rice where as I have seen it from the same amount of carbs from oats / potato. Plenty of other ways to get vitamins and minerals down.