First if your planning on doing alot of plants I suggest rehoming the silver dollars as they are plant eaters, herbivores. Adding alot more plants and or tall DW/decorations will help divide the tank and break some of the line of sight. Personally I'd rehome the barbs but if you like them then consider getting a larger school so you have at least 8 in a tank that big. Reason for this is when kept in a larger group aggression tends to stay within the group. Not always but often times this works. Veggies won't help with aggression but the Angels, Silver dollars and perhaps the Barbs will enjoy them. I use blanched zucchini and cooked, deshelled, slightly smushed peas in my 220g planted and all the fish love it.