Pond question

[gramma royale]

Mods, I know this isn't the right forum to post in, but I can't find the off topic forum. If one exists, can you move it there please?

My aunt and uncle have a pond in their backyard. It's been set up for about a year now, but they're running into some problems. The fish appear to have died off and there're large numbers of mosquito larvae thriving in the pond. If anyone has experience with ponds, can you tell me what kind of fish my relatives can add to the tank? Preferably ones that will thrive in outdoor environments and will also consume mosquito larvae. My relatives live in Irvine CA, so the weather is usually pretty mild here. Even in the winter, the coldest it will get is around 55 degrees.

Again, I know this isn't the forum to post in, but I'd really like some help on this subject. Even if you can suggest a pond or planted tank forum, that would be helpful as well. Thanks!

[JBM0676]

here is a really good pond forum, from my experience you can get what are called mosquito fish or even just some feeder fish to eat the larvae. if all their fish died off you might not wanna spend any money on good fish till you figure out what went wrong. feeder goldfish and comets are good buy at 10-15 cents and get the job done.
http://watergardening.infopop.net/3/OpenTopic

[Rendos]

Orfe's are great pond fish also. If you are getting mosquito larvae, sounds like it is pretty stagnant water. Add a pump to keep things moving. Mosquitoes don't usually lay eggs in rapdily moving water.

[rbaker]

Yeah, sounds to me like the water is stagnant. The fish might have died from lack of oxygen. They need a good pump to move the water and agitate the surface for good oxygen exchange...

Ryan

[BonsaiNut]

Give us some more info about the pond (size, depth, filtration, etc). I live about ten miles from your aunt and uncle and might be able to help out. I have a 7,000 gallon koi pond.

[gramma royale]

Thanks for all the responses.

The pond is actually an old jacuzzi that hasn't been in use for some time. They covered the jacuzzi with pond liner. If I had to estimate, the pond is probably 2,000 gallons with a depth of 3.5 feet.

In terms of filtration, there is none aside from tons of plants. The pond's plants do exceptionally well and consist of lilies, hornworts, hyacinths, and cabomba. I know agitation of the water will help, but it'd also kill the lilies. In all honesty, the lilies are really the pride of their pond, the flowers that bloom are incredibly beautiful.

With so many plants, could oxygen deprivation really be the cause of the fish's death? I guess it could be a problem at night and in the early morning, but the number of deaths would have been massive. Instead, the fish just simply petered out over a 2 year period. I attributed some of the deaths to a large stork or egret that flies by every morning. But the fish learned early on to avoid the birds by constantly hiding under the lilies. You rarely see the fish except in the evening.

However, the stork doesn't explain the rest of the die offs. My uncle told me that a large number of the older fish died off just these past few months. Given that goldfish are coldwater fish, could the heat waves this Summer have been the cause of death?

As for the mosquito larvae, I'll pick up a dozen mosquito fish to start off. I know they breed like mad, so I think a dozen is a good number to start off at.

[JBM0676]

i dont think the heat is a problem, with as many lilies as you say they have thats plenty of shade. my pond is in full sun all day with minimal shade from a few lilies and the fish are ok, but then again there is a waterfall that breaks the surface and cools the water and adds oxygen. my lilies have done well with the waterfall not too far from them.

[BonsaiNut]

Gold fish are super hardy fish (about the hardiest thing you can buy). Temperature shifts in a 2,000 gallon pond aren't going to be that dramatic either.

About fish deaths. If the fish disappear without a trace, you probably have a bird problem. Egrets and herons are KILLERS down here. I have lost many decent-sized koi to them (6" and up). They would certainly love small fish. The only way to protect your pond from birds is with netting. Trust me. If the fish disappear but you find some scales or blood, you probably have cats or racoons. There are also wild opposums and skunks here, but they don't both my pond. If the fish die and you find them floating in the pond, it is an internal issue (as if you couldn't tell).

Given that the pond has been setup for a few years, I would say that the likely culprit is oxygen deprivation, especially if the fish are dying at night. They need water circulation, even if it is one of those little statue frogs that sits on the side of the pool and "spits" a little stream of water. Water circulation like that will not kill lilies - I have a 2 HP and 3 HP pump that each turns over 1,000's of gallons per hour in my pond, and I can keep lilies without a problem - just make sure the lilies are outside of hard, direct current and the surface is not that agitated.

If they want to keep the "natural" pond look, they probably want to forget the goldfish (which get big and have high oxygen demands). Instead, I would recommend they go with some hardy tropical freshwater fish. Water temp will get down in the 60'sin the Winter, but no farther, especially if their pond is in the sun (which it needs to be if they are keeping lilies). See if they can find some hardy livebearers like guppies, which in addition to being prolific, pretty and small, will also eat mosquito larvae. There is a livebearer fish called a "mosquito fish" that is known for its appetite for mosquitos, but I don't know where you would find them in Southern Cal (plus they are rather drab looking).

[Fanatic]

Bonsai....any pics of your pond?

[BonsaiNut]

Here ya go. Pond is a little more than 20' long and about 10' wide. It is about 5' deep (you need deep ponds for healthy koi).

http://members.cox.net/bonsainut/Koi1.jpg

http://members.cox.net/bonsainut/Koi2.jpg