# Excessive Mulm...Repercussions?



## houstonhobby (Dec 12, 2008)

I think other than aesthetics there are no repurcusions. Mulm is dirt, ie all the bigtime organic chemical processes are done and the result is fairly inert, like MTS


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## Diana (Jan 14, 2010)

In an non-planted tank it would develop into Old Tank Syndrome. 
But the activities of the plants limits this nasty result. 

Old tank syndrome happens when a fish-only tank does not get enough water changes/gravel vacs. 
The organic matter (fish poop and food in varying stages of decomposition) builds up. 
The bacteria that decompose these materials use oxygen (which is replenished by water circulation) and some minerals, including carbonates, which are replenished with water changes (but this is a tank with not enough or no water changes). 
The bacteria population crashes. The mulm continues to build up, and ammonia becomes noticeable. With no KH (bacteria used it all), the pH drops, so the ammonia is present as NH4+, not so toxic to the fish. 
Over time, before the bacteria crashed, they were very busily making NO3. Levels can reach triple digits!

Now, you are looking at a tank with very low mineral levels, very high NO3 and NH4 levels. 
When you do a water change (presumably the tap water has minerals) the fish may die. Too great a change in TDS. 
When you add new fish, they die. The old fish acclimated to the toxic level of NO3 over time, but new fish cannot handle it. 
The solution is to do very small, frequent water changes, like 10% daily until conditions improve, and you can do larger water changes. Ultimately the mineral level rises and the fish acclimate to that, and the nitrogen is removed in all its forms. 

How this is different in a planted tank:
You are adding minerals, and monitoring the levels of KH and everything else. The way out of line nitrogen is much less likely to happen because you are monitoring it. The plants are using the nitrogen as fertilizer, too, so removing it from the water. 

I could see a few issues, though:

Some bacteria can grow when there is more mulm in the tank. Including the bacteria that cause fish diseases. 
Medications often can get locked up in organic matter, so do not hit their target. If you need to medicate a tank it is much better to do a thorough water change first. 
A thick enough layer of mulm builds up and can cover low growing plants, excluding light, so they can die. Some might just grow taller to get above the mulm. 
As organic matter is broken down in the tank it releases many nutrients for the plants including all the things we add as fertilizers, and CO2. This is the basis for a slow growing natural tank. The low levels and constant supply of nutrients is balanced with the relatively low light, and the plants are happy.


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## JeffHB (Feb 11, 2011)

*oh yeah..*

Two words same result....worms and planaria. been there and done it...don't let it happen its a pain in the arse to correct.


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## chad320 (Mar 7, 2010)

I never vacuum. I blow the mulm around when doing a waterchange and leave it at that. I dont ever get a huge buildup, even after a few years.


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## Brian3 (Jan 14, 2008)

That is because if we have a good big and potent filter or a good substrate we will have a tons of bacteria that eats the organic matter and the mulm only will go to the filter or deep in the substrate. Slow filters and no cleaning at all will do organic matter and mulm accumulation.


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## mistergreen (Dec 9, 2006)

It can trigger algae.


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## HypnoticAquatic (Feb 17, 2010)

if it can just accumulate on the leafs it will kill the leaf due to no light, ext ext. if you are getting a lot of build up of mulm you probably have poor circulation and or to much of a bio load that the tank can adequately handle


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## Cardinal Tetra (Feb 26, 2006)

IDK what happens to all of mine... I think it gets broken down and the plants suck it up or something. It is after all just fish/shrimp poo. 

My shrimp tank has soooo much of it though. It clouds up the water since the shrimp keep digging it up and I don't really do water changes. The shrimp seem to love the conditions though since their population keeps rising.


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## Brian3 (Jan 14, 2008)

I have aquariums El Natural style without this problem, another aquariums with this problems and high tech without this problems in my 4 years and 16+ planted aquariums. I think this most happend when you are in the middle of high tech and low tech. Low tech aquariums creates less mulm because we tends to use less fish, also have a active substrate with soil that helps to broke down mulm. In high tech aquariums I tend to do water changes, also have a potent filter with good flow (this is very important!!!) Potent canister filter is a must for high tech in my experience. Also my high tech have a lots of plants.


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