Mulm added to substrate

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Sumpin'fishy

Humble Disciple of Jesus Christ
Oct 16, 2002
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I keep hearing about adding mulm atop a layer of peat moss, then add flourite/onyx to a total of 3 to 4 inches. As I understand, mulm is just the garbage (slang term) you syphon from the tank with gravel vacs. I am going to be planting a 55 gal, so it's hard for me to picture saving (somehow) enough mulm to even lightly coat a 4 foot by 1 foot area. How do you preserve the mulm and save it until it is needed? Any other tips on prep work for the substrate is appreciated too! Thanks.
 

wetmanNY

AC Members
"Mulm"is a vague word for the softened detritus that forms when plant material is left to decompose until you don't recognize the shapes of leaf and stem. Mulm/detritus is still actively decomposing, however, using oxygen. Plants (and algae too) can't use phosphates and sulfates in the mulm until bacteria have separated the PO4 bits and SO4 bits from the big organic molecules. So mulm is plant-nutrition-in-the-making. It's on the way to becoming black "humus" which is better in the substrate than mulm.

In the lowest, least oxygenated levels of substrate, enrichments like mulm or potted plant compost (without extra fertilizer added) are controversial.

My own views are that 1. a substrate any deeper than what a horizontal network of plant roots requires is asking for trouble, and 2. in the substrate, colloidal silt or laterite--whether baked or raw-- providing binding sites for iron and phosphates etc, are more important than enrichments themselves.
 

Sumpin'fishy

Humble Disciple of Jesus Christ
Oct 16, 2002
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Savannah, GA
Thanks for the input. I have heard from enough people that use mulm that I'm willing to try it myself. Although I'm appreciative of the extra info, I'm just wondering how I can collect and store enough mulm to be effective in layering a 55 gal tank.

Colloidal silt? Binding sites for iron and phosphates.....I think you are shooting above my level of understanding in this arena. It sounds like you know what's going on though! :)
 

wetmanNY

AC Members
Sorry. Colloids are platelike microscopic particles, the ones that make wet clay slippery. Their surfaces bind some important plant nutrients that you might prefer to have in the substrate rather than in the water column. It\ron and phosphate are two.

The mulm is decomposing to humus. That's the end product of plant material that can't be mineralized by microbes.

In the lower levels of the substrate, decomposition will be anaerobic. If oxygen is truly absent there can be some hydrogen sulfide produced from organic matter ("mulm") decomposing.

Get a look at some of the threads and links on substrate at www.thekrib.com/ or www.skepticalaquarist.com/
 

plantbrain

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Apr 27, 2001
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I don't consider mulm the least bit controversial. It's always been standard procedure for me and many LFS's. Adding it works. I lost count as to how many times I've set tanks up with it (just about every tank I've ever set up all my life has had it added). I told folks to do that when I was a kid working at a LFS years ago. I was told to do it by an old salt.

My substrate can be up to 12-16 inches deep in large tanks and 7-8 inches in rear spots in regular smaller tanks and slope down to 1 inch in the front.
I've never had a single substrate issue except once when a cable heater cooked an Aponogeton bulb and it died. I vacuumed the gravel around the area and that was that.

Folks that move slow bulb (Crinums, some Aponogetons, Lilies/Lotus etc) plants around too much can suffer this fate.
But these plants do quite well in anaerobic substrates, that where they live in nature, most aquatic rooted plants for that matter.

Adding mulm does one primary function, adds the good bacteria and instantly cycles your tank of which the filter and the substrate possess the largest colonies of bacteria. Lots and lots of surface area. Roots invade these regions and the bacteria have associations with the plant roots. This speeds up this bacteria/plant root colonization.

Aquatic plants release _large amounts_ of O2 to the areas around their root zones(this is how they live in anaerobic waterlogged soils).
They also relsease H+ to add reducing power to absorb nutrients.
Peat helps this process(H+), taking some load off the plants till the tank is established and going well.

Both of these additions simply give the tank a jump start.

Adding peat adds some reducing power to the substrate that will develop as the tank/substrate ages anyway. This allows the nutrients to be more available for the plants.

A 20 gallon tank will get about 1 liter 2 liter of decanted mulm.
One good sized handful of _ground_ peat.
Top with flourite or onyx sand, 2-4 inches. You can slope the gravel front to back or side to side etc.
That's it.

You can dry the mulm out and add that also. Fresh is _much_ better. I've dried it in the past and added it. Too much work:)
Go down to a friends, LFS and and bring a bucket and vac. I'm sure they will not mind a nice gravel washing for free.
Let the bucket sit for 5 minutes of so, pour off the clear liquid.
Save the goop. Add it it right away to the substrate and then get the tank set up and filled. If you need to store it, keep it in a dark/warm place.

Save a little to feed into the filter, that will instantly cycle the filter(or you can loan the filter out to place where you plan on getting the mulm for a couple of weeks if you have the time etc).

Rinse flourite /onyx sand only 3 times in the bucket(1/2 a bag at a time). Add that to the tank, it'll be dusty still but it will be dusty after 10 washes, so don't worry about that, the tank will clear fast. Just do the three washes.

Now you are done.

For non CO2 tanks I add 4x the mulm, 4x the peat. The flourite is at least 4 inches deep.

Regards,
Tom Barr
 

wetmanNY

AC Members
Anaerobic decomposition in the substrate: apparently even whether it's controversial or not-- is controversial !!

Like Tom Barr, I've only had a single brush with the hydrogen sulfide he's referring to when he mentions "substrate issues" and it was in a rotted-out Aponogeton bulb, too! I think he'll agree that fears of H2S are overplayed among us. H2S is being produced in microzones all through the aquarium, and constantly being oxidized to harmless sulfate by the bacteria living right next door. Same is true in the substrate layers. Sulfate's what most plants use rather than sulfide.

I'm sure there's always plenty of "mulm" and "detritus" and "floc" as well as dark "humus" in my re-used and all-but-unwashed lower substrate layers, so I suppose I underestimate the lengths one might go to, in order to collect some. I always add a little peat, as Tom Barr does.

But even though my substrate is never a foot deep like plantbrain's, I don't actively encourage anaerobic decomposition deep in the substrate, or a substrate deeper than what the rootzone really needs.
 

plantbrain

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Yea, I think folks over play that H2S thing a bit much.
Aponogetons and Crinums are the only blackened substrate areas I've ever found. I've seen other tanks long ago that had it, but the plant's lived about 3 weeks till they died in a brown gelatinous mush.
I "fixed" a couple old dupla substrate that used too fine sand and had not be set up properly for a few friends. It was severly compacted
and had poor plant growth.
If the plants are dying, adding them to the substrate might provide a good place for H2S. Or if growing well and then they die from nutrients/CO2 issues etc.

My notion about the deep substrate is that it has more surface area, more bacteria, room for roots to spread out, more stable/less disturbed especially at the greater depths(this allows the bacteria to recolonize fast after a replanting), allows more nutrient holding capacity, allows the roots to pick what depth they wish to grow into. A nice reductive/anoxic bottom layer that's deep is better protected by the depth. The entire substrate need not be 6 -12 inches deep etc but it's fine to have deep areas and shallow areas.

Substrates were an obsession for many folks 10 years or more ago. There are many variables and it's generally difficult to test substrates. I've spent many years with soil, peat, kitty litter, and most of the other substrate materials and cables/RFUG's and other flow rates through them. But a relatively simple method can test the substrates for optimum plant growth.
Different substrates can be added to the same tank and diffirent tanks. If you keep the rest of the parameters the same, you can measure the the before and after weight of the plants.

I did not do this in a very controlled manner. But, I have done it enough to know enough about what works better than another or not. It just takes time and trying different system over years to figure it out. Plant looks, not just growth is a very big consideration here also.

If you like aerobic substrates , using RFUG's are quite good. These grow plants well. Not as good as flourite etc, but good nonetheless, about like cables.

I don't know about whether I would say that it's a bad idea for new/old folks to keep the minimum depth of gravel for the substrate. I've never had/seen any issues nor have a number of planted tanks/newbies etc that had deep substrates. I have never gotten any comments of a blackened subs from anyone on email come to think of it.

The only detraction I can think of for a deep substrate is lost of tank space or height, seeing a bunch of gravel on the front glass pane.

I just slope the gravel back and slope ot down to the trim edge in the fronts and side typically. This gives depth to the aquascape and adds some deep areas of gravel.

It's fun using a fair amount of gravel like Flourite since it does not shift around like sand nearly as much. No flat gravel tank syndrome.

While obsessing over the gravel for years, I figured out good CO2 levels and then finally nutrients in the water column. Less importance is placed on the nutrients in the substrate when the nutrients are available in the water column. This can be tested for much easier and produces excellent growth.
Plants will take it from water column if it is available. If the water column is "lean" the plant will allocate more root growth and uptake from the substrate.

So even with no nutrients in the substrate, you can grow some pretty nice plants. But allowing the plant access to both areas, this gives the best results. I think it's about 20% roots and 80% water column depending on the plant taxa for good growth. Some other research showed(Freshwater Ecology 2001) 15%/85% or so for the Root/water column optimum for 25 aquatic plants so that figure is not too far off I'd say. So a balance of both methods gives the best result, IME, IMO and as to what the current research that's out there indicates.

Regards,
Tom Barr
 

Sumpin'fishy

Humble Disciple of Jesus Christ
Oct 16, 2002
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Savannah, GA
I appreciate the responses, guys. I got my questions answered and learned even more than expected. As always, a pleasure!
 
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