# Possible solution to extreme filamentous diatom outbreaks



## zeldar (Jun 24, 2009)

I haven't been very active on the forum in years, but thought this information could be beneficial to people going through what I have. I've set up probably 10 planted tanks in the last several years and each time they are overtaken by filamentous diatoms within 2 weeks. This stuff grows! I'm talking several inches a day. See pictures of the insanity:

















This was happening in every tank I set up! I tried everything, from changing substrates, to lighting, to water, to ferts. Nothing helped slow down the diatom growth. I even read to let the silicates run out in the tank and that will end the diatoms run. The longest I let one of these tanks run was over 6 months and it was still growing diatoms like a champ. I was living in Houston and finally chalked up that the diatoms must be a Houston water problem so I quit planted tanks. 

Moved to Dallas at the beginning of the year and setup a new tank. Everything in the tank was new. Substrate, hardscape, plants. I even replaced the Eheim sponges. Sure enough, a couple weeks after setup, filamentous diatoms. I was going crazy, siphoning them out with an air hose only to have it engulf the tank 2 days later. I was about ready to shut her down again when I was talking to an old planted tank buddy about it. He suggested throwing out the Eheim Substrat as it is made of glass which could be causing the silicates that the diatoms were feeding off of. So I replaced the Substrat with Seachem Matrix. That was a week ago. I don't see one strand of diatoms anywhere in the tank! The whole time, the ONLY thing I didn't replace besides the filter itself and the tank was the Substrat! Trust me, I did tonsss of research on diatoms but haven't seen anyone mention Substrat as being a possible culprit. 

I did see several people going through the pain I have so I made this post hoping it saves some people some hard ache. If you are at wits end with filamentous diatoms, try swapping out your Substrat for a non glass based biomedia!

Shoutout to the OG *onefang* for figuring this out for me. The forum was a better place with you on it.


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## OVT (Nov 29, 2011)

Thank you very much for the post as I am going through similar experience. Guess what media is in my Eheim?
Something else for me to try.

I have such diatoms in my 2 of 8 tanks. All Eheims have the same media. I feel like I am still missing something.


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## zeldar (Jun 24, 2009)

I had 5+ year old Eheims with stock media on all my planted tanks so it might be an issue of the Substrat getting old which exposes the silicates. Back when i bought the Eheim's new, I never had a diatom issue. 

I setup a 2211 on my brothers tank and it never had a diatom issue, but it was a newer filter. I also had a opae ula tank with no filter that obviously didn't have this problem (its brackish water). Only thing that is slightly off was my shellie tank I had setup a year ago. It was running an Eheim with Substrat. It didn't get diatoms either, but I was using an acintic light fixture so maybe diatoms don't grow in that environment?


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## OVT (Nov 29, 2011)

This might be reaching a bit, but here are our commonalities:my tanks with diatoms have used media that has been sitting dry for about 1.5 years and then washed and re-used. The tanks with no diatoms have exactly the same media, about the same age but that has been used continuously, without sitting dry. I wonder if the drying-off period changes the media's structure?

I happen to have the same exact Eheim media that has never been used, just sitting in a plastic bag. I will use it on one tank and see what happens.

Eheim media has a stellar reputation and, I bet, we are not the only ones re-using it. I nevereven thought twice about it. I saw a couple of similar reports on TPT and I wonder what is their media history.

Live and learn, constantly.


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## Surf (Jun 13, 2017)

Diatoms don't form filaments. Diatoms are a form of particulate algae. they can turn water milky green or a particulate dust that settles on leaves and substrate. What you have is hair algae with some other form of algae mixed in to make a portion of it look brown. I have seen dark green, light green and a greenish white hair algae in my tank

Hair algae thrives in aquariums with nutrient deficiencies. when there isn't enough of a nutrient or nutrients for plants growth slows and may stop. Hair algae in contrast can still get enough to grow rapidly. When your plants can grow as fast as they want hair algae tends to die back. I think you should be looking more at your fertilizers than what is in your filter or your substrate. To that end it would be helpful to list the fertilizers you use, and your water hardness (GH), alkalinity (KH), ammonia, nitrite, and nitrate levels from your water tests. 

I have not uses the Eheim substrate. I did a search for Eheim substrate and from what i have found it is sintered glass with a lot of pores in which bacteria can grow in. it designed to aid biological filtration. Sintered glass probably doesn't have a lot of nutrients in it so it wouldn't address a nutrient deficiency.


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## OVT (Nov 29, 2011)

You make a lot of good points @Surf.

I have been using EI in all of my tanks for a long time now and I tend to over-plant. That being said, a fresh API test kit should be in tomorrow and I will start testing.


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## zeldar (Jun 24, 2009)

I actually sent a sample of the diatoms to onefang a year or so ago. He put them under a microscope and confirmed they were colonial diatoms. I was getting them in tanks with new aquasoil and EI dosing so don't think there is anyway there wasn't enough ferts.

Diatoms do form filament like structures as they "colonize" in an end-to-end manner. https://en.wikipedia.org/wiki/Fragilaria


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## Surf (Jun 13, 2017)

As single cell diatoms grow the shell gradually gets smaller. When it gets to small the shell changes allowing it to get back to full size again. The end result is week point in the ribbon does form periodically causing it to fracture into smaller lengths. According to this document they typically have a length of 100 micrometers long. 


A single strand of hair algae can reach a length of about 2 feet long. I have pulled strands out of my aquarium that were that long. However Hiar algae often gets tangled and will often look like it does in your tank. And it has sufficient flexibility to be tied into knot without breaking. IN most cases if you have one variety of algae you often have others. So I would not be surprised if have hair algae with some diatoms trapped within the tangled mess of hair algae.

Most fertilizers mixes used for EI dosing don't have any calcium sulfur or chlorine in them which plants need to grow. Often tap water has these in abundance but not always. Calcium deficiencies do come up commonly on this forum.


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