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[APD] RE: mulm accreation rates
> >Mulm is not a good thing really except in small amounts in the substrate
> >large amounts in a non CO2 tank substrate. Too much can be bad and place
> >larger demand on O2 and organic fractions of nutrients which take more
> >to become available to plants. Works well in non CO2 tanks, but in CO2
> >enriched tanks, not so well in general.Things move too fast.
> >Reminerlization takes some time and less light to work well for plants.
> Tom, this is a radical new thought, at least for me. I've been reading
> posts over the last couple of months about the wonders of mulm, although
> those were all in the context of a low-light tank.
Too much of anything can be bad. Well, except for planted tanks(but don't
ask the spouse).
This can lead to lots of organics, drain on the O2 levels, redox levels
that are too low and produce sulfur instead of Fe/Mn reduction and
Depends on the __rate__ of accreation though.
> My high-light CO2 plant tank is now 2 1/2 years old. It has always had a
> moderate or higher fish load. The Flourite substrate has never been
> vacuumed, except for surface accumulations (no gravel swirling). It's
> pretty thick with mulm at this point. It's on a 50% weekly water change
> regimen (aka Barr System).
> Conventional wisdom is that we don't deep-vac the substrate in plant
> Does your statement above advise otherwise?
Generally yes, but as you uproot over time, you pull up a lot of mulm.
Also, when the mulm settles down in the substrate, it's there to stay
unless you pull it up. Bacteria are going remineralize it. It all depends
on the loading rate of organic matter.
Too much mulm in some spots can cause dead zones where some plants just
will not grow etc. Vacuum these spots.
Mulm is not some wonder thing but certainly helps in starting up a NEW
tank. Otherwise less is better in my view.
In established tanks that are a year or two old, VACUUMING certainly does
not harm anything IME/IMO if you use something like flourite etc. Sometimes
general tank reworks are done and I'll typically do this when I move a tank
or design a new layout etc.Tank seems to do a little better, certainly
cleaner for awhile.
There's no reason why this would be bad per se either.
With Flourite or other highly porous substrates, vacuuming will disturb the
verticle layers of bacteria etc, but not the bacteria in the internal grain
The other thing is that since more of the tank's load is now inorganic,
this aids in growth of the plants vs the algae which can use the organic
fraction faster/easier than plants since they generally have to wait for
the bacteria to remineralize the organic fraction.
If you ever get a spot where you have sulfur smells, this means that there
is so much organic matter down there, it exceeds the O2 levels to decompose
it, then you get that black nasty smell. But you MUST have a fair amount of
organic matter to do this. Deep substrates without any organic
material(Carbon source) will not go anaerobic or produce sulfur. Mulm has
already been oxidized GENERALLY.
But consider all the root pieces that get buried and left behind when
uprooting? That can add some, not enough in most cases to casue that. So
these pieces never make it up into the water column where there is a lot of
This remineralization process in a thriving O2 rich pearling tank will
ocurr at a faster rate based on a few things it seems to me.
1# Surface area, porousity of the substrate sediment, aerboic/anaerobic
spaces will help speed this vs plain old sand substrates.
2# O2 levels, supplying high O2 levels help bacteria to perform better to
oxidize the materials rather than keep them anaerobic. Anaerobic is okay,
but at less light, slower growing tanks etc.
3# Periodic vacuuming an older flourite or onyx, Eco Complete or what have
you type of substrate after a year or two poses no issues and is desirable
Tghis is NOT to say you tear the tank down or do it all at once etc, you
can if you want, but a 1/4 section of vacuuming per water change will clean
things up for you and I think most folks will find it helps their tank's a
fair amount to do this once every year or two.
This keeps it clean, keeps algae off of it, allows you to readjust any
slope and exports any excess mulm etc. I like to have cleaner substrates
when I replant and not a bunch of detritual mulm floating all over each
time I uproot. I have to vacuum that up anyway.
This whole thing sort of gets back to whether to add organic matter, N, P
to the substrate. I've found over the years that adding inorganic chem's to
the water column improves the plant's growth a great deal while removing
the organic fraction or just not having it, eg RFUG filters tended to help
and improve growth when using CO2 at 20-30ppm. Adding organic matter, NPK
to the sub did not improve plant health, growth unless something was
limiting in the water column. Then you have a situation where the plant
will rely more on the roots, and the substrate.
Many people like the idea of balance and using the organic fraction and
having break down slowly and used by their plants.
This works best with the non CO2 approaches is my point if that is your
goal. Give the time the cycle needs to complete, adding CO2 speeds that up
and people need to balance that rate with export of mulm, plant biomass,
water changes etc.
Most folks already lightly vacuum their substrate anyway, deep vacuuming is
not going to change that really, but you will have to uproot and replant
that section which is not bad peroidically anyway. Just working your
garden, pruning, replanting, keeping things in clean regularly and in top
shape helps.This is just getting back to that basic notion.
> Dave Millman
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