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RE: Fertilizer question
Nathan Wittmaier wrote me asking some follow up questions regarding my
advice to Melissa and her fertilizer options. His questions seem germaine
enough to answer publicly - I'm sure that there are others who are wondering
the same things.
> What does "mixed" mean? What kind of a proportion of laterite:gravel is
> generally recommended here for the lower third? I see a lot of comments by
> people which I had been reading as laterite & that's it for the
> lower level.
> I'm not getting that impression here ....
By "laterite" I mean a type of highly weathered soil with a relatively high
iron content (the source of the red color) found in tropical or once
tropical areas (did you know that the Arctic was once tropical?). This
"weathering" has taken place over geologic time (thousands to tens of
thousands of years). I don't use the term "laterite" to refer to just any
red soil or clay.
By "mixing", I mean just that - you put 1/3 of the gravel into the tank,
sprinkle it with the laterite, and stir.... sort of like making mud pies as
a child, but much more "adult".
You cover this laterite/gravel layer with the other 2/3 of your plain,
washed gravel. You end up with a kind of upside down cake (sorry for the
food analogies, I'm hungry...), with the laterite on the bottom.
How much laterite you use depends I guess upon which brand you use. Dupla
recommends one amount, Carl Schoeler recommends a much higher amount. My
personal experience is with Duplarit G. I don't really think it's critical
HOW MUCH is there, within broad limits. But I'd recommend that you follow
the manufacturer's recommendation. Apparently, Duplarit G will soon be
available from Monolith Marine Monsters (m3).
Note that there are several products currently available on the market which
are called "laterite", and the archives and newsgroups are full of reports
of people finding a local red soil and then claiming that it is "laterite".
I don't know if they are true laterites, nor do I vouch for their
effectiveness. The archives DO have good things to say about Substrate Gold,
from Carl Schoeler, but it is different from Duplarit G in that I believe he
adds a fertilizer component to it (which is not in Duplarit G). But
apparently it works well and I would venture to guess that it could be used
interchangeably for Duplarit G.
> 1. Third laterite and gravel mix topped by two-thirds gravel.
> (I'm assuming
> for a total cover of about 2-3 inches.) This requires water column
> fertilization and focuses there rather than further substrate
> fertilization (added layers of this, that or the other or spot
> with Jobes spikes or clay balls or what have you). Would water column
> fertilization taper as the laterite gathers plant goodies in the
The total depth of your substrate depends upon the size of your tank and how
high it is - I wouldn't recommend a 6" layer of substrate for a 15 gallon
tank, but it might be appropriate for a 200 gallon tank. In a 120 gallon
tank that was 24" high, around 4" of substrate depth should suffice (a lot
depends upon what you are trying to grow - a large swordplant might
appreciate more depth). I'd use about 1" - 1 1/2" of gravel/laterite on the
bottom and 2 1/2" - 3" of clean gravel covering it. Plant roots DO travel
quite a distance, and a healthy root system will pull oxygen into the
In a tank set up with laterite under the gravel, the "goodies" as you refer
to them come from the fertilizers you add to the water column - over time,
the additions of fertilizers are STILL going to be needed, but you may find
that after a while you might need to adjust the amount and/or supplement
certain minerals more than others. The nutrient ions will diffuse down
through the gravel and be attracted to the the laterite, sticking there
until they are absorbed by the plant roots. As the substrate matures, and
fills with mineralized mulm, this effect generally increases, and that might
mean you would need to add less fertilizer. (Mineralized mulm and fish food
is actually a wonderful fertilizer.)
> 2. Clay or kitty litter. (Assuming with a top layer of gravel -
> inch or so -
> to hold things down and collect mulm.) Some water column
> fertilization here.
> Not a broad-band (down to micronutrients) fertilization, though. Does this
> include the "red art clay" style or is that a part of the next category?
I've used "Red Art" clay - and I'd class it with the "kitty litter crowd".
Actually though, while the actual contents of most kitty litter can be kind
of hard to determine, the mineral composition of "Red Art" clay is readily
available from the manufacturer (they gave it to me anyway). Turns out that
there are quite a few good things in "Red Art" clay for plants. Clays and
kitty litters are best treated like laterite in that they should be covered
by a nice thick layer of clean gravel. One caution however - "Red Art" clay
is sold in powdered form - you would NOT put in a 1" - 1 1/2" layer of solid
clay in the bottom of the tank - you merely sprinkle some over the lower
layer of gravel and then mix it in, as you do with laterite/gravel.
> 3. Soil. Obviously requires research about soil types, etc. Also, likely
> requires that layer of gravel to keep things down. Not so much
> water column
> fertilization. The substrate is intended to do the trick for the
> most part.
> No combo here with clay/kitty litter layering? I'm going to
> assume that this
> is primarily a technique for those plants that get a high proportion of
> their nutrients from the substrate. ... or at least to assure their strong
> health. Question: Is this generally a technique which would require CO2?
> Maybe that's a dum question .... Another dum question: Commercial potting
> soil is a no-no, right?
Whether or not you HAVE to add supplemental CO2 has more to do with the
light level over the tank. Think of it this way - the substrate, and the
mineral nutrients contained within it, are a sort of storehouse which will
be drawn upon by the plant roots as needed. How much they need depends upon
how fast they are growing, and that is determined by how intense the light
is and how readily they can obtain Carbon. Life on Earth is Carbon based,
and in order to make new tissue, plants need Carbon - which they get from
Carbon Dioxide (that's a simplification, but true enough for our purposes
here). If there isn't sufficient CO2 in the water column, or in the
substrate, the "engine" will stall, unless the plant is capable of obtaining
Carbon from bicarbonates (but that causes another set of problems and is
generally best avoided in the close confines of an aquarium). If the plant
growth stalls, algae get a chance to overtake the whole system and use the
nutrients that are there.
You can have a very nice planted tank without additional CO2 - just keep the
light level at around 2 watts per gallon. You limit what you can grow, and
the plants will grow more slowly, but it does work.
There are no dumb questions - only dumb answers - most commercial "potting
soils" today are artificial (peat+sand+perlite+vermiculite+fertilizer) and
they are usually too light in weight (peat, perlite and vermicultie will all
float in water) so they are messy and the added fertilizer makes the stuff
WAY too rich for use in an aquarium (but perfect for petunias).
No substrate technique _requires_ the use of supplemental CO2 - that need is
determined by the amount of light, and the type of plants being grown.
> 4. Spot substrate fertilization with Jobe's sticks, etc. Here,
> I'm going to
> assume focus on water column fertilization and primary use of plants which
> get much of their nutrients from the water column. Maybe not a good
> assumption. (That's why I'm asking.) :-)
Spot fertilizing, whether with Jobes sticks or enriched clay balls can be
very good for heavy root feeders - I do it all the time for my Crypts and
> 5. (My addition) Flourite/Profile. I'm not sure if I'm understanding what
> this is, but it would be a stand-alone substrate type similar to the
> laterite/gravel type. Again, attention to the water column. (Assumptions
Flourite works beautifully as an aquarium substrate. I'd love to get my
hands on some Profile, which is apparently similar. Yes - when using this
sort of substrate, you should fertilize the water column. And even though
you haven't asked, I wouldn't recommend using Flourite + laterite (or kitty
litter, or soil, or peat, or.....)
> 6. (Another addition intentionally left out?) Sand with...... Now more
> assumptions. Sand can be in or out kind of like your standard gravel.
> Neither should affect nutrients except for collecting mulm. Two key
> problems: packing and disturbing it creates a mess. One note is
> to watch for
> sand which could affect pH.
Sand is for sand-boxes and making castles at the beach. I don't like sand in
an aquarium substrate. The particles are too small and will interfere with
circulation of water through the substrate.
> 8. Peat additions. I noticed you only mentioned this with the soil style.
> I've seen a lot of people bandy around putting peat in here and
> putting peat
> in there. Your recommendation suggests otherwise. Why only with the soil
> style? I'm guessing that in some ways, peat is kind of like the spot
> fertilizing with Jobes sticks .... if it's used in spots rather than as a
> layer. As a layer, you would classify it in the soil group?
People bandy things about a lot. You have to remember that there are many
ways to successefully grow aquatic plants and there are many different types
of aquatic plants. Just because someone's cousin says it worked for his next
door meighbours' brother doesn't mean that it will work for me or for you.
Don't believe everthing your hear or read. I've used a combination of peat
moss, half rotted beech leaves and some mineral topsoil to grow Cryps, but I
wouldn't try it in a show tank. Peat will act as a binder for heavy metals
and can reduce the effects of toxicity in some sub-soils. Peat is NOT like a
fertilizer. I only use peat in conjunction with a clay subsoil, and then
only a VERY small amount.
> Sorry to just recap, but combing the archives often leaves me (a total
> newbie) with a mish-mash of ideas which lose their distinction. I want to
> try to get a better understanding of what the particular, distinct methods
> are ..... and what plants they are good for, so that once I run
> into my bag
> of money and choose my method, I know what plants are best for my tank.
That's why I recommend that newbies stay away from complex, hybrid
approaches. Don't just read a lot and take a bit from here and a bit from
there. Pick ONE approach which has worked for a LOT of people and is
relatively simple. Once you have a year or two of experience, then you can
venture into unexplored territory.
An aquarium substrate doe NOT need to be highly fertile to grow beautiful
plants (actually, it shouldn't be highly fertile). Laterite + plain gravel
works wonderfully and has done so for many, many people. If you can't afford
to add supplemental CO2, don't sweat it - just keep the lighting limited to
around 2 watts per gallon and chose low light plants.
> Well, I was going to send this to this list, but after considering, I
> figured I would try just sending it to you, because I don't want to spam
> everybody with too much of the basics
From a lot of recent posts, I don't think it at all inappropriate to go over
the "basics" once again. People need to be reminded of the KISS principle
every now and again.