Larvae In Pond Filters / What Are These Worms?

Recent Consult

Larval caddisfly on filter box material
Larval caddisfly on filter box material

The guy:

My name is B___K___ from Cookeville, Tennessee. I attended your talk at Splendor Koi in Marietta Ga, the other month.

I have a question concerning my pond. My pond is about 10,000 gallon with 25-30 fish. Chuck helped me to set up this pond and provided all hardware and filtration.

My question is this spring I have noticed a type of bug that attaches itself to all the filter components, skimmer baskets, skimmer filter racks.

I have several pictures that should help you identify the problem. I would like to hear your recommendations to solve said problem.

My Response:

Hi B____!

Larval caddisfly on filter box material
Larval caddisfly on filter box material

Those are the larval form of some fly, like a caddisfly, or Mayfly. They won’t be a year round thing.
Young koi will eat them on sight.
Hence they should only be in fishless areas e.g. filter boxes, infrastructure.
They’re harmless although certain species can be a liability to fry (very baby fish).
They’re not a symptom of anything.
They need no address or remedy.
If you dislike them, a couple Bream in the filter box will consume them readily.

From the Guy:

Thank you for your response.
The fish are doing fine so it was not an issue to them.
In the filters I also find worm / larva. With a high pressure washer, they get blown off and out of the plastic filters and racks and baskets. Every two to three weeks I take the pressure washer down the creek bed and over the water fall to remove algae. I also use algae-away to reduce the algae propagation.
Again thank you for your response.

B____ K______