Koi pond maintenance

April 11, 2014 2:32 PM

I have two questions about koi pond maintenance. 1) How do I know if the UV light in my filter is burned out, and 2) how do I not kill my fish?

1) The pond in the house we bought has a Laguna pond pump (one of these models) and I'm wondering if the UV light may be burned out -- the water clarity has gotten pretty poor and there's a decent amount of string algae on the walls. How can I tell for sure?

The light is not supposed to be plugged in if water isn't running through the unit via the pump, and I know I'm not supposed to look directly at the light anyway. So how do I figure out if the light is functioning? (The alternative is that the light is fine but I'm not backwashing the filter often enough -- once every 1-2 weeks right now. Just need to know for sure.)

2) The koi -- four HUGE guys -- have been dormant since we moved in in November, but I suspect they'll be coming around soon. Taking care of dormant fish is the easiest thing in the world. I'm worried that once they start acting like living things again, I'll kill 'em.

What is your best advice for koi pond/koi fish maintenance? (Tips on useful websites would be great too, because I haven't found any.) My knowledge right now is limited to a) feed fish and b) periodically backwash the filter. Oh, and there's a water fall on either end of the pond, so I think we're okay on aeration.

posted by mudpuppie to Home & Garden (6 answers total)

Response by poster: When I said "Laguna pond pump," I meant "Laguna pond UV filter."
posted by mudpuppie at 2:34 PM on April 11, 2014

I think yellow highlighter ink drawn on white paper will fluoresce under UV, that might be an easy way to test.
posted by pseudostrabismus at 2:35 PM on April 11, 2014

UV lights don't just emit UV, they emit other parts of the spectrum as well. If you turn it on in a dark room, and don't notice any light coming from it, then it is burned out. (Obviously, you should take appropriate precautions and not look directly at the light.)
posted by 517 at 4:12 PM on April 11, 2014

First of all, relax. Koi are not that easy to kill. I have lost exactly two fish in the eight years I've had my pond, neither due to anything I did or did not do. There have been baby fish hatched to replace them.

A "spring bloom" of algae is normal. My pond goes through a phase of too much algae every spring, before the tree that shades it leafs out and the waterlilies cover most of the surface and shade it out. You want a little algae to nourish the fish and oxygenate the water.

Are you in touch with the previous owners of your house? They would be a good source for maintenance tips; in fact, I am surprised they didn't leave instructions.

It would be helpful to know these things: How big is your pond, in gallons? Is it indoor or outdoor? Is it in sun or shade? Are there plants in and around the pond (other than algae)? Is there decaying plant matter on the bottom?

A pond is its own little ecosystem and the key to keeping it and all its life forms healthy - and the pond looking good - is achieving a balance. My advice? Don't feed your koi too much. They can get by quite well on algae. Don't go crazy checking the pH all the time and adding chemicals. Use natural, organic products to boost the breakdown of organic waste; I like this stuff (there's a fall/winter prep version too). Ponds are way easier to care for than many people think. There really is not much more to it than cleaning the filter, in my experience. BTW, I don't have a UV filter, and I've never missed it.

There may be a pond club in your vicinity; that would be a good place to get information. I'm surprised you found nothing worthwhile on the Web, because that hasn't been my experience. Here's one. I don't agree with everything there - for example, I have had the pond cleaned once, and only because I got lazy about the fall/winter prep, and I don't do pH tests or worry about the amount of water that gets added (I have an autofiller). I have a clean, clear, healthy pond and happy fish, so I must be doing something right.
posted by caryatid at 4:19 PM on April 11, 2014

Beware of birds if your pond isn't netted.
posted by srboisvert at 6:49 PM on April 11, 2014

About netting: my pond is about 1000 feet from the South Platte River, as the heron flies. My pond is netted for maybe a month in the fall to catch leaves, and open to the air the rest of the year. I have never lost a single fish to predators. The one time I did see a great blue heron scoping out the pond (hard to miss a four foot tall bird with a six-foot wingspan that comes soaring over the yard like Mothra to land on your roof!) I ran outside with my camera so fast that I scared it off, and it has never been back. Every pond should have a built-in "fish cave" where the fishies can hide from predators like raccoons and fishing birds, and the fish have the sense to hide there and wait until the predator has gone.

While I know that there are ponders who swear by having their ponds netted year-round, I have never found it necessary, and it certainly isn't attractive or convenient. Birds can get caught in or under the netting and drown or thrash themselves to death. Part of the fun of having a backyard pond is all the wildlife it will attract. I've had coons, foxes, skunks, hawks, flickers, and who knows what else I haven't seen visit my pond for a drink. I once saw a squirrel fall in and swim to shore, cussing a blue streak, which was just as hilarious as it sounds. Netting would have prevented all that.

So sure, net it if you want to, but you're not necessarily risking your fishes' lives if you don't.
posted by caryatid at 8:34 PM on April 11, 2014 [1 favorite]