How to clean a pond of algae?

November 17, 2005 12:51 PM

Help me rebuild an ecosystem! I'm looking for a specific little algae-eater . . .

I have a small "pond" on my patio that is roughly 5' x 3' and about 1' deep. I recently had to empty all the water out of the pool to make way for another patio project. In doing so I removed a population of little shrimp-like critters that thrived in the pond. These were very small, only about 1mm in length. They were translucent. They swam by twitching their tails back and forth. And, there were perhaps thousands of the little guys peacefully coexisting in the pond.

I refilled the pond with water about two weeks ago and there is now a film of algae growing on the surface. Without the little shrimp there to eat the algae it appears that my pond is doomed! I need to find out what these creatures are called and where I can purchase them. I'm in San Francisco if location makes any difference. Help me rebuild my ecosystem!

posted by quadog to home & garden (13 comments total)

They're brine shrimp. (Sea Monkeys are one breed). You can buy a big vial of them (with hundreds of thousands of eggs) at any aquarium specialty shop-- people raise them to feed to fish that need live prey.

If you want to go nuts, there are websites that sell them by the bucketful with guaranteed hatching rates,
posted by Mayor Curley at 12:57 PM on November 17, 2005

6th avenue aquarium, on clement, is your spot
posted by alkupe at 12:58 PM on November 17, 2005

Sounds to me like you were breeding mosquitoes! You don't want those back. Get yourself some coi.
posted by Pollomacho at 1:08 PM on November 17, 2005

Mosquito Larvae

Were these the fellows? If so they'll be back on their own.
posted by Pollomacho at 1:10 PM on November 17, 2005

Er, if this is a freshwater pond, those were not brine shrimp. Brine shrimp live in, well, brine. Salt water.

Chances are, unless you scrubbed the pond raw with bleach and so forth, or let it dry completely, there are a few of the little guys hanging on still. Especially if they are not something you put in there deliberately the first time; they're probably something native. Give them a chance to rebuild their numbers and things should get back to normal.

You can also go to a nearby local pond that looks like it's doing well and take a big sample bucket of mud, weeds, water and so forth, and dump it in your pond. You'll undoubtedly get some more of your little copepods in that sample.
posted by Rubber Soul at 1:12 PM on November 17, 2005

Sounds to me like you were breeding mosquitoes!

Nope. They definitely were not mosquitos. If they were my entire condo would have been invaded this summer and I didn't see a single one of 'em.

unless you scrubbed the pond raw with bleach and so forth, or let it dry completely, there are a few of the little guys hanging on still

I didn't scrub it down but it did get pretty dry. It'd be kind of a miracle if a few were able to hang on.
posted by quadog at 1:23 PM on November 17, 2005

You probably had a nice colony of Daphnia going. follow Rubber Soul's advice and you will have them back in no time.
posted by a22lamia at 1:32 PM on November 17, 2005

Try to get in touch with a local aquarium club. They might know where to obtain a wild colony of daphnia to reseed your pond with.
posted by sid at 1:34 PM on November 17, 2005

Er, if this is a freshwater pond, those were not brine shrimp. Brine shrimp live in, well, brine. Salt water.

I was lazy and didn't read the question carefully enough-- I thought that the poster had just moved into the place and the ecosystem was a deliberate thing. Sorry!
posted by Mayor Curley at 2:03 PM on November 17, 2005

I second the suggestion for the aquarium on clement. Those guys have everything.
posted by cali at 2:18 PM on November 17, 2005

Those are probably zooplankton (although 1mm seems a little large - oh, right - daphnia - but there were probably zooplankton, which also eats algae, in there).

I did an undergrad ecology project - some ponds had algae, others didn't. The zooplankton helped clear algae, but the biggest factor was fertilzer runoff (ready bioavailable phosphorous and nitrogen was greatly helping the algae grow).

There are these *really* fine-meshed nets that look like a dunce-cap. I spent a few weeks rowing boat back and forth through various ponds trailing that sucker and collecting zooplankton. You might be able to find something similar and wave it around in a algae-free pond. The distribution of zooplankton will vary depending on the time of day.
posted by PurplePorpoise at 4:03 PM on November 17, 2005

definitely Daphnia. Don't know where you can get them commercially but some pond water from a healthy looking pond (clear, with plants) is probably your best bet. They will likely come back on their own eventually but a little physical algae removal and the re-introduction should help speed things along and prevent the algae from choking your pond to death in the short term. They typically need plant cover to survive btw, and if you have too many small piscivorous fish they will eat them and consequently they need more cover to survive in useful numbers so consider removing small fish for a while (or permanently).
posted by fshgrl at 4:50 PM on November 17, 2005

If you can't find the little shrimp again, you can always buy a few Chinese algae eaters (near the bottom of the page). They are pretty much impossible to kill.
posted by 517 at 7:53 AM on November 18, 2005