pond question

So, I've being trying to convince my parents to have a pond. They have turtles in a big tank, but I feel like the turtles look big in it as well. I want them to have more room. The water gets dirty fast, but they won't listen to me because they said it's okay since the turtles are hardy and can...

So my sister is building a pond in our backyard with the goal of eventually getting Koi Fish for it… (she’s got all the filters and pumps for it to house fish and it’s got a waterfall attached) and we were wondering how water changes would work with fish. Could we fill it up with normal water...