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Dupla only?? + Steve's fertile substrate

Steve wrote:

>I'm not saying that laterite can ONLY work with the Dupla system, I am
>saying it works only because it IS part of a total system, the Dupla

I think that you are defining the "Dupla system" rather broadly.<g>  I
suspect Kaspar Horst might not agree.  
>By that I mean is that the overall strategy must include providing all
>of the nutrients required by the plants. In the case of the Dupla
>strategy, you have iron and trace nutrients being provided by the daily
>Dupla drops. In the case of folks using laterite with other water
>fertilizers such as TMG, I presume that the iron and trace nutrients are
>being supplied by the Tropica Master Grow, PMDD or other preparations. 

And why does that make them the "Dupla Method"?  I don't think _anyone_ can
grow aquatic plants (at least for very long<g>) without meeting all their
nutritional needs in one way or another.

>Remember that several of these experienced hobbyists also use methods
>such as Jobe's fertilizer sticks to add nitrate and phosphate in the

Sorry if I'm being dense, Steve, but I don't see your point.  You _did_ say:

>Laterite works only because it is part of the whole Dupla system.

Laterite has worked for me for years.  In slower growth systems, there are
enough macronutrients provided trhough fish food/fish waste.  In strongly
lit, CO2 supplemented tanks, I occasionally need to supplement these, at
least with my current fish load. (Believe me, I never did when I had Discus
in the tank!<g>)  I don't consider my tanks "Dupla Method tanks, although I
respect the Dupla method as a viable one.  

I re-read what you wrote about phosphate, and although I won't argue one
way or the other whether phosphate must be supplied is a limiting growth
factor in _your_ tanks,  I _am_ sure it's not  the limiting factor in the
majority of tanks of the majority of aquatic gardeners I've visited with. 

If it _is_ necessary for phosphate to be available via the substrate, one
way or another, with or without the rest of the "Dupla Method", it gets
there in laterite based tanks.  You only need to look at how well how many
of these tanks do over the long run to see that the basic needs of plant
growth are being met.  

BTW, I have used laterite other than Dupla's, adn I have used Dupla
laterite without their "rooting tablet"  While the rooting tablet
definitely gets plants off to a quicker start in a newly set up tank,
(Dupla without the rooting tablet works second best) I've had very
respectable results with the other products as well.

>I've wondered where these huge Salvinia plants come from that we
>occasionally find in aquarium stores. When I bring them home and
>propagate them floating, I always get plants only 4-5 mm across. A big
>clue came when I started using Salvinia in my hyper-eutrophic killie
>tanks. Suddenly I started getting BIG Salvinia!! In my large aquariums I
>suspect there simply isn't enough phosphate available to the Salvinia.
>My guess is that the huge specimens we see in the stores are actually
>grown in eutrophic ponds or mud holes in full sunlight.

It may well be possible to grow big Salvinia in polluted tanks... I've
often seen that when my tank water is macro-nutrient poor I can't grow
Duckweed at all, and Salvinia does poorly.  However,  Huge Salvinia is the
norm in the wild.  When we got the wild collected plants for the "Ponds"
exhibit at the NEA, all the Salvinia collected had leaves that were Quarter
sized, tightly folded,  and in long, strongly connected chains.  That's
just the way the plant grows under good, natural conditions.  Once you've
seen the "real thing" aquarium, or even goldfish pond grown stuff looks
pretty anemic!<g>

>The largest Crypt wendtii that I ever grew were grown on an extremely
>fertile 3 layer substrate which was a mixture of about 40 pounds of
>gravel, 8 kg of iron rich pottery clay,  4 kg of earthworm castings,
>about 5 kg of vermiculite and enriched with 60 grams of FTE and 150 ml
>of Hanging Basket & Planter Fertilizer 14-14-14 Controlled Release
>Fertilizer. Whoa!!! Very, very fertile but what a difference! Another
problem with this
>tank was the jungle like appearance it would get a couple of weeks after
>each pruning. I had Crypts the size of medium sword plants. 

We have C. wendtii plants in several of the school tanks where we do _no_
macronutrient supplementation (beyond lightly feeding a low fish
population) that routinely grow into dense stands 20" tall.  In my
experience, light levels are very important in determining the height of

>If I did it
>again, I'd leave out the 14-14-14 fertilizer, most of the FTE and use
>much less earthworm castings. I also probably won't use vermiculite
>again since it makes a mess when uprooting plants. The aquarium was
>stable for over a year and I only tore it down after it got infested
>with a plague of Oedogonium (fur) algae when I was away on vacation for
>2 months.

Wait a second, you said that in the only 1 year period you had:

> I had nitrate concentrations of
>over 100 ppm. Phosphate concentration stayed relatively low at about 0.5
>ppm (although I have trouble believing my own notes). Ammonia levels hit
>1 ppm about a month after submergence so I added a biological filter and
>the ammonia quickly subsided. I had to fight blue green algae and green
>unicellular algae like pea soup. Some types of plants seemed to have
>difficulty coping with the low redox and high nutrient concentrations in
>this substrate especially after a pruning. 

Sorry, Steve, but I sure wouldn't call that a stable tank!  I know this is
subjective, but I have to honestly say that as much as I preach patience, I
wouldn't have the patience for that! (particularly if it meant tearing the
tank down at the end of a year in any case)    
>One last word of caution; beginners probably need to master the basic
>husbandry techniques before experimenting with fertilizer in the

I couldn't agree more.

>On the topic of basic husbandry, we've always assumed that
>its better for beginners to use chelated iron dosing. I'm just
>suggesting that MAYBE we should reconsider our first step advise. It
>might be easier for newbies to follow a detailed but clear multi-step
>procedure than to master the chelated iron dosing art.

What about not even suggesting that they _buy_ an iron test kit, and learn,
instead, to watch their plants for iron deficiency.

>Following the recommended dosing
>instructions for some of the more concentrated fertilizers like Flourish
>also can lead to excessive iron (in my experience)!

Yes, that's true.  Mastergrow suggests, and I think this is a good idea
with all commercial fertilizers, start with 1/2 the recommended dose, then
work up based on the response of your plants.

>I also wonder if we do newbies a service by recommending 2-3 watts per
>gallon. I know at _least_ one expert who recommends starting with low
>light levels. Another famous expert gets lush growth using 1.6 watts per
>gallon!! ;-)

Our school tanks run around 2w/g.  This seems to be manageable for most
people and allows for the use of all but the most light hungry species.  I
don't really see _any_ reason to go much _above_ 3w/g... I have yet to fail
with a plant where I could attribute the failure to a lack of light at 3 w/g.

Karen Randall
Aquatic Gardeners Association