@Panzer13 Dave just described for you the difference between a garden pond and a dedicated koi pond. As he said, some of us love our ponds to grow plants and fish while others are only interested in the koi. At 200 gallons, you definitely have a garden pond!
Since your pond is small, you may want to focus on plants that stay small. For example, there are a number of dwarf varieties of water lily that would do fine in a smaller pond. I have a small patio pond that I drop a dwarf variety lily every year and it does great. There are small varieties of many other types of plants as well - just do a search for "dwarf pond plants" and pay attention to the size the plant can attain. You can also plant things outside the edges of pond that will grow over the sides and hide the edges - things like creeping jenny or vinca. Lots of possibilities! Post some pictures and we can make more suggestions!