Plants solve all issues.
A more involved option is to remove all the rock and then rebuild mortaring the rock in place. That gives you control. Loose rock moves over time. A lot of DIYers don't want to use mortar for many reasons. They think it takes a lot of skill, or believe myths about being toxic in a pond or freezing. Instead they want to use glues, foam, goops. That's really unfortunate because mortar is by far the easiest way (assuming a good result is the goal), cheapest, best lasting method. It's why professionals don't use goops. Yes, many pond builders do use foam, but to me getting money for something doesn't make them professionals.
If you go with mortar the trick to a natural look is to not have any visible mortar. Use really thin mortar beds. You're not really trying to glue then together, you're just filling the uneven gap between rocks. That's exactly how a dry stacked wall is made except they use small rocks instead of mortar. Mortar is way faster and works great. You do still need to do what dry stacked stone wall builders do, fine just the right rock for each space. So it's not like laying bricks, just using the next closest rock.
Another nice thing about mortar is should you ever want a new pond the rocks can be removed with a few taps, the mortar cleaned off a little and the rocks reused. Goops can be a huge pain to remove.