# Mulm- Good, Bad, Ugly?



## Rana (Apr 27, 2013)

My planted tank has a light-colored sand substrate, so the dark brown detritus/mulm that builds up on top is, uh, _noticeable_. So far I've been siphoning out only small amounts with my water changes, since my DIY gravel vac also sucks up a lot of the sand if I get too enthusiastic with it.

I'm wondering, how do others feel about mulm? I've been reading some people saying they never clean it up, that it's just free fertilizer as it gets broken down. Others say it's bad to let it build up since an aquarium isn't a full ecosystem, so it's doing more harm than good by growing bacteria & fungi.

And still others say it isn't harmful _or_ helpful, they just get rid of it because they don't like the appearance or else leave it be since the look doesn't bother them.

I assume this is yet another topic that will never get a clear answer, but I'm still curious to get some opinions from the folks here! 


Personally, I am leaning towards using a chopstick to stir up the sand and mix the mulm in so it looks less obvious, at least towards the front of the tank. I have approximately a zillion Trumpet snails in this tank so they should help keep things churned up as well. Not sure if it'll really do anything to "enrich" the substrate or not, but I only have one actual root-feeder in my tank anyway (and it just got a fresh root tab not too long ago) so that's not a big concern for me right now.


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## WellBetta (Apr 24, 2020)

I only got into planted tanks a year ago, so I'm also curious what other people do. For what it's worth I leave the mulm around my plants, but during water changes I suction any that ends up in the open area of the tanks where it's most visible because I don't like how it looks. My plants are growing pretty well in my low tech tanks, and I haven't had any trouble with fungi or bacteria as far as I can tell.


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## Mr Grumpy (Feb 28, 2020)

> I've been reading some people saying they never clean it up, that it's just free fertilizer as it gets broken down


I use gravel and never vacuum the substrate, anyway my tanks are too heavily planted
However not vacuuming the substrate only if you have lots of plants and Malaysian Trumpet snails
Can you imagine trying to vacuum this?


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## Rainbo (Nov 23, 2015)

It's ugly, but not harmful. Whether to leave it or get rid of it is up to the fish keeper.


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## RussellTheShihTzu (Mar 19, 2013)

I have sand so it has not place to go and remains on the surface. I hate that mulm so I vacuum.


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## Capers7 (Mar 17, 2019)

I have multiple tanks, but only 2 with light colored pool filter sand. The one that does NOT have corydoras is the only one that does what you are describing. I have to vacuum that one regularly, or it looks like a bunch of brown dust bunnies have moved in. If your tank can handle it, get a group of corys and they will turn the mulm under for you and keep the substrate in better shape. I do vacuum when the mulm gets so deep I can see it in the glass building up to the top, but all of my tanks are fairly heavily planted so the waste from the mulm gets absorbed. It is my understanding that without a lot of plants, excess mulm can get toxic after a while. How about some pictures? I love looking at other people's tanks.


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## Phish Head (Jul 23, 2019)

That's the reason I won't use a light substrate - I don't want to look at mulm or deal with it. 

I used to vacuum it but the tank has grown in too much (aquasoil) so I guess the mulm is just part of the tank's ecology now  

Sent from my Pixel 3 XL using Tapatalk


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## Mr Grumpy (Feb 28, 2020)

Hi
Substrate...... something for the plants to live in
Vacuuming............ Something you do to the carpet in your home.
Mulum..........Free fertilizer for the plants and free food for my Malaysian Trumpet Snails

Anyone want to give vacuuming the substrate in this tank a try?


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## Rana (Apr 27, 2013)

Loving the variety of answers, it's just about the spread of opinions I expected! So many things in aquariums come down to personal decisions in the end and I think it's just great to have a variety. 😄


And, @Mr Grumpy I don't think _anyone_ would be eager to try vacuuming that thickly planted of a tank! I can't even fathom how you fit them all in there in the first place, or how they've grown to fill all the gaps.

My own is much less full, though I'd love to someday have a tank that's totally wall-to-wall plants. Until then I'll just have to keep battling my poor decision of using light sand on the bottom.


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## Mr Grumpy (Feb 28, 2020)

> And, @Mr Grumpy I don't think _anyone_ would be eager to try vacuuming that thickly planted of a tank! I can't even fathom how you fit them all in there in the first place, or how they've grown to fill all the gaps.


The plants grew in, the real fun part? getting the root tabs into the substrate.


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## Mr Grumpy (Feb 28, 2020)

@Rana

You could get 2 pots of Staurogyne repens and 2 pots of Alternanthera Reineckii ( tissue culture plants ) and stick them in the sand in a few months you wont see the sand anymore, Both these plants do OK in low to medium light and need no CO2.










PS

see there is substrate there LOL.


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## Rana (Apr 27, 2013)

Mr Grumpy said:


> @Rana
> 
> You could get 2 pots of Staurogyne repens and 2 pots of Alternanthera Reineckii ( tissue culture plants ) and stick them in the sand in a few months you wont see the sand anymore, Both these plants do OK in low to medium light and need no CO2.
> 
> ...


I will have to keep those plants in mind! I don't have the budget for new plants right now, but I wouldn't mind some plants that will "take over" a bit.

And haha, I guess there _is_ substrate in there after all! Could have fooled me.


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## milererik8 (Nov 1, 2021)

If you don’t want to use any filters to get rid of mulm, you can get yourself different kinds of catfish like Ancistrus, Corydoras, Loricaria, or Pterygoplicht, etc. They all serve the purpose of keepers of cleanness as they eat algae, sludge, and mulm. Also, they may be useful for other bigger co-habitants as they are feed by external pests of fish. For example, In nature, young platydores often help larger species get rid of parasites on the body, which is not typical of freshwater fish. As for myself, I have Synodontis bought at https://www.aquarzon.com as well as Pterygoplicht. All types of Synodontis are very beautiful. Their coloring often includes spots or stripes. Well-developed dorsal and caudal fins often have a veil


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## Ragtatter (Dec 16, 2021)

Personally? I'd get a little bit of a darker substrate, and mix it in with the surface of your lighter substrate for a more mixed/dappled appearance to make the mulm less noticeable. It's great for the plants.

Edit: Sorry for the necromancy. It was only after posting that I realized this thread was from like two years ago....


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