Thanks for all the ideas. I know some people don't like the symmetry at all but I'm exactly on the opposite end - I like it and I put quite a lot of effort to achieve it. It wasn't easy to get matching branches and I think I will keep the way it is for now. Thanks thoughHi!
First, the roots look very nice, you have a lot of possibilities.
In my opinion, if you still want to keep all together, maybe if you bring the small one in between the others, you will have a deepness effect but without symmetry.
The golden ratio is also related to the position of the main rock or root in relation with the lenght of the tank (somewhere at a third of it).
Another solution is to split them, and to get a main root and a small, second one. But it is up to you. Good luck!