filterless currentless pond

Aquarius Keeper

I have some pond questions for anyone with any experience

I'm house-sitting for my parents in Los Angeles this month, and we've had an oooold fish pond in our front yard as long as we've been here - It's stone set into the ground - I'm guessing well over 60 years old. There have been fish in it sporadically (and even populations of frogs back in the 80's when the climate wasn't so dry) - though it has never been consciously maintained by anyone - right now empty except for an overgrown water-lily population and at least a foot of crud (10+ years of fallen leaves etc...) at the bottom...

It's 6 feet in diameter, I'm guessing 1.5 feet deep - so about 320 gallons (does that sound right?)

Anyway I was passing it today and was surprised to see a Goldfish in it! My mother added a few feeders about a year ago to keep the mosquito larva in check - I didn't think they'd last - there just so much crud in there - but I guess the pond still supports life.

So now I'm thinking it might be fun (well, disgusting, but fun in the long run) to clean all that gunk out of the pond and restore it to it's former glory and add a few more fish.

The only thing is, once I'm gone nobody is going to maintain it, it will be a strictly "nature takes it's course" sort of thing. The pond is a standing body - no current, and I'm pretty sure my parents aren't going to want to run a power line out there to install a filter. So we're talking about 320 gallons of unfiltered standing water with a ton of water lilies, algae etc...(when I brought in some water to test, it was teaming with little organisms)

Has anyone tried to keep fish happy and healthy in such an environment? I know we've had some fish live for years in this pond in much worse conditions than I would be restoring it to - still I'll bet stocking it would be a sensitive issue as it's such a static ecosystem? (nitrate levels are only slightly above 0ppm at present)

Any thoughts are appreciated.

Thanks!

Jonathan

iamntbatman

If there's no filtration going on, I'd be careful about removing all of the gunk in one go, as that's probably where a ton of the beneficial bacteria are.

If your estimates on size are correct, the pond could probably support a decent population of Goldfish, but I wouldn't get Koi. Koi need about 1000 gallons per fish when they're full grown as they get to be over three feet long as adults. You could also try mosquito fish.

Aquarius Keeper

I miscalculated (and have since edited) my original post - I actually got a tape measure to hit bottom and it's only 18 inches deep, so about 320 gallons if my math is right.

I don't want to flood it with fish - I'd want them to be as comfortable as possible (and Koi just scare me) - so I'm happy to be conservative - what do you think is a healthy number?

(and thanks for the advice vis a vis the gunk - I was worried that if I started mucking around in there the whole ecosystem would collapse...)

Jonathan

iamntbatman

I would say 50 gallons per adult fish would be good, so six total. It would probably be best to put a few more than that in there, as you can count on them being unhealthy when you buy them and on some getting eaten by wildlife.

You probably already knew this, but the comet Goldfish sold for a few dollars a piece at pet stores are the exact same as the ten cent feeder Goldfish.