# Is Mulm harmful?



## Knight~Ryder (Dec 2, 2007)

I just found out what Mulm is.

I know I asked before what all the brown stuff on my filter was. No one explained what it was

Is it okay to leave my filter there with all that mulm built up on it?
Is it safe? Anything more I need to know about this stuff?


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## emc7 (Jul 23, 2005)

The thing with a filter is to keep it flowing. If the flow is slowing, rinse the cartridge. If the tubes are slimely inside, use a brush to clean them. I think of "mulm" as any decaying plant matter. Its not dangerous in itself and can be helpful to feed plants. But it can cause high nitrates, clog filters, potentially lower ph (esp. if it contains peat like stuff out of potted plants' pot). Brown stuff on filter could be algae or uneaten food, but it doesn't matter really. Keep the filters flowing and watch the level of the nitrates. If they are getting high, clean up what you can. If they are low (because of plants), you can let more build up.


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## Knight~Ryder (Dec 2, 2007)

This meansI need to clean the whole filter that hangs on my aquarium. What is the best way to do this?

Take the whole thing out and wash/scrub it?


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## Guest (Dec 10, 2008)

emc7 said:


> The thing with a filter is to keep it flowing. If the flow is slowing, rinse the cartridge. If the tubes are slimely inside, use a brush to clean them. I think of "mulm" as any decaying plant matter. Its not dangerous in itself and can be helpful to feed plants. But it can cause high nitrates, clog filters, potentially lower ph (esp. if it contains peat like stuff out of potted plants' pot). Brown stuff on filter could be algae or uneaten food, but it doesn't matter really. Keep the filters flowing and watch the level of the nitrates. If they are getting high, clean up what you can. If they are low (because of plants), you can let more build up.


I disagree. In my mulm experience as very dangerous, to not only the fishes, but the algums. The thing with mulm is it can increase the nitrate m3 to dangerous levels, causing fish death or messyumn. I agree mulm isn't very harmful, but if you let it build up it can be devestating.


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## emc7 (Jul 23, 2005)

Scrub it in the sink with a brush or "green scrubbie". It isn't a big deal, but the longer you let it build up, the harder it will be clean.


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## emc7 (Jul 23, 2005)

> as very dangerous,


I would say "it depends" in a small, overstocked tank any additional decaying matter is risky. In a large tank with lots of nitrate-eating plants, its not important. People with heavily-planted tanks often let it build up rather than break down the tank to clean it.


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## Knight~Ryder (Dec 2, 2007)

emc7 said:


> Scrub it in the sink with a brush or "green scrubbie". It isn't a big deal, but the longer you let it build up, the harder it will be clean.


Looks like I got a job on my hands in the morning. 
I just cleaned the thing about 2 months ago....


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## Lupin (Aug 1, 2006)

Your filter will get clogged if you keep the mulm building up.


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## emc7 (Jul 23, 2005)

http://freshaquarium.about.com/od/termsandtables/g/mulm.htm
Here's a definition for mulm.

The brown stuff on filter could be mulm, uneaten food, or the brown diatoms that you scraped off the glass. Rinsing the cartridge in running water is usually enough to get it off. Don't scrub or rinse the biowheel, just leave it in the tank when you clean the filter. If you get more "mulm" you get ouf of the tank, you won't need quite as big a water change to keep the nitrates down. But don't go overboard, obsessively cleaning your tank and filter can cause "mini-cycles". You might also try moving the brown-tipped plants to directly under the center of the light to try to get them to go green.


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## jones57742 (Sep 8, 2007)

Folks:

I have very recently run onto something relative to my HOB's.

Obviously the mechanical and biological mechanical filtration media should be cleaned in WC water but cleaning the housings and other parts in hot tap water appears to help extend the period until the next cleaning. (Please note that a firm bristle toothbrush is very useful also.)

TR


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