TIL that building a small koi pond in my backyard was a terrible idea

I dug a 4x6 hole behind my garage in Phoenix last summer and filled it with water and four goldfish... by week two the water was green and the mosquitoes had claimed it as their own private resort. Has anyone actually managed to keep a backyard pond from turning into a swamp without spending a fortune on pumps and filters?

3 comments

3 Comments

jake_owens26d agoMost Upvoted

Did you put any plants in there? Because without plants that thing is just a toilet bowl in the sun. I tossed some hornwort and water lettuce in mine and it went from swamp to something that kinda looks like a pond. Still have to scoop out leaves every few days though. The mosquitoes went away once the goldfish got big enough to eat the larvae. But now the goldfish are basically pond monsters and I have to break ice in the winter.

michaelchen26d ago

I read somewhere that the whole "pond ecosystem" thing is basically a myth unless you have at least 60% plant coverage (which I thought was just something made up by pond guys trying to sell you more plants). Also, the depth matters a ton in Phoenix because shallow water heats up super fast and turns into algae soup. I heard from a guy at a garden center that you need at least 18 inches deep for any kind of thermal buffer, otherwise the sun just cooks everything. He also said that without aeration (like a cheap bubbler stone or a little solar pump), the water goes stagnant and that's when the mosquito army moves in. It's a bummer because a pond sounds so nice, but it's basically a full time job unless you go all in on the setup.

jamie_smith26d ago

Right, so that 18 inch depth thing, that reminds me of my neighbor Frank. He dug a pond in his backyard years ago, maybe 12 inches deep at best. He was so proud of it, stocked it with those little feeder goldfish from the pet store. Within a week the water was this weird green color, like split pea soup. Two weeks later the fish were all belly up. He drained the whole thing and filled it with dirt the next weekend, turned it into a flower bed. Still cracks me up every time I walk by his house and see that sad patch of petunias where he tried to have his pond paradise. I guess the moral is you gotta listen to the guy at the garden center.