Your water looks good! I understand your daughter-situation (i have a little girl too), however, over time, you will probably continue to have issues here because of your stocking situation. Goldfish are omnivores (they eat veggies & meats)-if the danios are small enough to fit in his mouth, snacking will continue to be a possibility. Perhaps you can consider getting another tank for him if you are not willing to rehome him? I would also offer him a piece of plain cooked broccoli daily (flower part) to give him something to pick at all day-replace with fresh floret after 24hrs (or sooner if its eaten). This may help curb his tendencies for right now its not a permanent solution, especially as he continues to get larger. Good luck!