so i have a temporary koi pond that im really just using as a grow out tub/pond for the fish for my future koi pond , it has a lot of plants and good filtration plus i plan on adding more. i also plan on setting up a biobucket filter. it has a few different fancy goldfish, 1 butterfly koi and one regular koi, some wild minnows, 2 mollies, some platies, and 2 guppies. theres also some snails and wildlife like frogs and bugs. everyone does great together with no signs of stress. the water parameters have been stable and great. all the fish eat right out my hand. but anyways to the point im kind of stumped on how im supposed to set up a overflow system on this pond and on my future pond. it sits right under my roof so water flows right in. ive just covered if with sheet metal or tarp when it rains but i really would like something more efficient and also budget friendly. any tips would be greatly appreciated.