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Dr. B.
Dr. B., Board Certified Veterinarian
Category: Vet
Satisfied Customers: 22584
Experience:  General practice veterinary surgeon with extensive experience in a wide range of species.
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Subject: Pond Fish, On cleaning my pond filters (3) the

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Subject: Pond Fish,
On cleaning my pond filters (3) the other week-end I noticed between the sponge mats a large number of "shrimp" like things, on cleaning these were washed away, are these a sign of a problem?, all fish appear well

Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today.

If you were seeing living "shrimp" like critters in the filter and not on the fish, I'd be highly suspicious that these are just larvae from your local insect population. We often will see insect larvae in ponds as their parent insect takes advantage of the small convenient body of water. And these small larvae can easily end up sucked into the filter. Common water based larvae include mosquito larvae (example), dragonfly larvae (example), water beetles, and mayflies.

In these situations, they do not usually cause any issue with the fish (some fish will actually eat them for more protein). We would just want to consider double checking water parameters (as a good baseline step) and consider possibly clearing the filters a bit more frequently until the weather cools. And while I do invite you to post a photo of these critters so we can ID them together (
To post them, you can either use the wee paper clip on the tool bar (How To). Or you can post them on a 3rd party site (ie Flickr, Photobucket, etc) and paste the web address here), I would be very suspicious that these are just non-harmful insect larvae sharing the pond with your fish and no sinister issue here.

I hope this information is helpful.

If you need any additional information, do not hesitate to ask!

All the best,

Dr. B.


If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and hope to see you again soon! : )
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Customer: replied 3 years ago.

thanks, ***** ***** me piece of mind, as it's what I thought

You are very welcome.
I am glad that I could give you that peace of mind.
Have a great day,
Dr. B.