Floating clumps of algae-too many goldfish?


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Hi everyone. I have a natural swimming pond that is 3 years old now. The first 2 years we had LOTS of tadpoles in the spring, and they ate all the algae off the wood and the plants looked robust. We introduced about 10 goldfish about 2 years ago. They have reproduced like crazy and now there are dozens of small goldfish, the original ones are pretty big (>6 inches long). We had few tadpoles this year, and now we have clumps of floating algae. I’m afraid we’ve got more organic material than the filtration can handle because of the excess fish waste. My husband disagrees and says the pond is big enough to handle the number of fish we have. (Disclaimer: We did have a lot of leaves fall in the pond last year that didn’t get removed, and are decomposing in the regeneration zone. Will cover with a net this year!)

The pond has a swimming area that is 10’ x 20’. The regeneration zone extends 6’ out on the long sides and 10’ out on the short sides. We estimate total volume of about 17,000 gallons. We have cattails, reeds, water celery, aquatic mint, water lilies, water clover. Replanted hornwort this year because it died off over winter, but it isn’t doing well, is covered by the green sludge. The lilies don’t seem healthy, they have few leaves. The whole pond is in full sun, we added sails this year to give some shade.

The filter is an eco pump, pulls water through the gravel in the regeneration zone, returns into the swimming area, and we run it on low 24 hours a day. The water is crystal clear, pH is 7.4, 0 ammonia, nitrates, nitrites.

I think the ecosystem is okay, but don’t know if I should try to remove all the floating sludge. Husband wants to vacuum the gravel and bottom of pool. I‘m afraid that would disrupt the biofilm/periphyton layer.

So many questions! Thanks in advance for any advice y’all can give!

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Jhn

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The fish probably are contributing but I doubt they are the root of the problem, more than likely it is a combo of fish, not cleaning the leaves out of the pond, needing more plants and lack of circulation. You could clean the junk out of the pond bottom, that won’t really do much to the biofilm in the pond even vacuuming the gravel shouldn’t do it, just don’t scrub the sides or gravel clean.

I would keep your pump running 24/7 but crank it up. I don’t know how strong it is gph wise but in a pond your size I would try to get at least the volume turned over once per hour if possible more. The plants you chose are some good ones for nutrient export/banking, but you need more of them, in a pond as large as yours. Especially, the water celery, mint, can add forgetmenots, creeping Jenny, watercress.....cannas/taros are annuals in most places but grow quickly and consume a lot of nutrients. Pickerel rush, lotus are some others that will do well. Just watch the lotus it can take over.
 
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Very cool idea!

Essentially when you have an overgrowth of algae, you have excess nutrients in your pond. You need more plants or more filtration to remove the excess nutrients. Could be the fish, could be the humans, but most likely your thought about the leaves is the most accurate. Organic materials decaying in the pond will cause an overgrowth of algae.
 
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addy1

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I vote for a lot more plants!
 

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