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Little brown "worms" in my filter?

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I started a new tank just over a month ago. It's a 46 gallon tank that I added treated water and water from my 65 gallon tank to. My 65 gallon tank is heavily planted and has been great for years with no problems. My new tank is also heavily planted and I have gradually been adding fish. I just tested my water yesterday and all is well, other than the nitrates being a bit high, but no cause for alarm - I did just add some Cherry Barbs, so that could be it. I add beneficial bacteria to both my tanks, usually biweekly, every second water change. I fertilize and use biological filtration.

I noticed there are small brown "worms" in my new tank's filter. They are definitely multiplying. They are in the filter uptake tube and in the sponge and biological media. This leads me to believe they are beneficial and feeding off of the debris caught in the filter. They are nowhere else in the tank. Nor are they in my 65 gallon tank. I have never seen this before. I frequently move plants between the two tanks, and the new tank is is stocked with mostly propagated plants from my 65 gallon tank.

I have tried to find out what they are on the internet, with no luck. Most people just respond with guesses.

I have attached a (not so great) picture of my biological media within my filter. You can make out some of the worms, they resemble fish poop kind of, but definitely are not.

My tank is otherwise healthy and growing great! In fact, the new Angelfish that I got about a month ago have already spawned twice!!

Does anyone have a name for these 'worms'??

Thank you,



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Discussion Starter · #16 ·
Problem solved people! I answered my own question. But I am glad I asked either way!

They are a beneficial bacteria that live in sheaths. They oxidize iron and magnesium and thrive in high organic matter environments. The tank is just over a month old, so new, and I have been using liquid fertilizer weekly, which is high in iron which aquatic plants love. Either way, I have obviously been using too much! The bacteria are totally useful, which is good to know.

It never hurts to ask!

Oh, here's a great article with pictures about them. Leptothrix is the name I think, or "Iron Bacteria".

Fertilizer: sometimes less is more!
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