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Re[2]: trimming and richer substrate


Please allow me to clarify a couple of points. Earlier I wrote:
> A better substrate would be one containing clay and or an amount of soil 
> mixed with sand in a lower layer. If you are using soil or other organic 
> additives, my opinion is that there is not much point in using laterite.
> If you're going to use the real laterite, your strategy is going to be
> to avoid sources of organic acids (like some soil types) because you want
> to use an automatic pH controller to precisely control CO2 injection.

What I'm trying to say here is that I think there is not much point in 
mixing an expensive laterite with other materials for a substrate. There 
are other sources of iron oxides such as micronized iron and soils which 
are cheaper and easier to find. The big point about laterite is the things 
it doesn't have in it which you MAY not want. This means relatively low 
amounts of organic material (it gets in there eventually from the fish), 
organic acids and nutrients. Real laterite is also relatively low in 
silicates but it's doubtful that this is important. Stick to one strategy 
and don't go mixing things together wildly thinking more is better. These 
strategies are quite different and you need to understand nutrient 
requirements before experimenting too much.

The reason why the choice of substrate is affected by your algae prevention 
strategy is that organic substrates tend to release very large amounts of 
nutrients such as nitrates (and phosphates) into the water for the first 
few months. You need to regulate the amount of chelated Fe you use quite 
closely and try to provide an environment without contamination by 
filamentous algaes. That implies bleaching the tank and plants prior to 
installation or getting them from a known sterile tank or taking emersed 
cuttings. Perhaps my experiences with a rich substrate are exacerbated by 
my strong lighting. I suspect that it may be easier to maintain a soil or 
peat tank under low or moderate lighting conditions.

My first experiment with a rich substrate mix using earthworm castings, 
clay, gravel and osmocote is a disappointment. While I was away, the tank 
became overgrown with a fur algae probably from some delicate plants I 
introduced without bleaching. I also experienced early problems with green 
water and cyanobacteria which made the early stages of the tank a 
maintenance hassle. Growth was very fast and I have some huge Crypts from 
this tank. I suspect I will have to bleach them and restart the tank with a 
relatively infertile substrate. I may try adding several SAEs to this tank 
to see what happens.

My latest substrate experiment is going much better. The tank does have 
contamination with brush algae however it does not seem to be a severe 
problem. No problems with green water or cyanobacteria. This is a deep 
substrate. I used small amounts of micronized iron and fritted trace 
elements in the bottom layer mixed with a lot of sand. I was concerned 
about iron and trace element toxicity so that's why its relatively deep. 
The middle layers have more organic material. It also has a commercial 
product called basin soil which has sand, peat and other materials. This is 
all described in a previous posting on the APD earlier this year. There is 
quite a bit more sand in this substrate since I didn't want high nutrient 
levels and I wanted to reduce the rate of diffusion of nutrients coming 
from the substrate. In contrast, low fertile substrates work by allowing 
nutrients (ie fish poop) to work INTO the gravel. With organic substrates 
you prefer that decomposition and release of nutrients is very slow and 
that diffusion of nutrients out of the substrate are also slow.

Growth in this tank is not as rapid as the other tank but the health of the 
plants is very good. This tank is still producing bubbles from the 
substrate after several months but it doesn't appear to be a problem. It 
now looks like a very nice tank; I better photograph and video it quick 
before something disastrous happens!! I've also greatly reduced the density 
and number of species plantings in this tank and opted for several 
specialty plants like E horemanii, E barthii, and a very large and very 
small crypt which could be C blassii and C nurii but I forget which is 
which and could find no reference to identify them with in any of the 
Baench atlases. Is there a better reference for Crypts?

Another reason for making this substrate deep is that I'm hoping to make 
the substrate self-sufficient for Fe. The plants don't seem to be suffering 
from lack of Fe but the H stricta still shows some signs of Fe deficit and 
slow growth. Pennywort also shows Fe deficit and floating plants grow very 
slowly. It looks like many plants like Crypts can tolerate low Fe levels 
and get their requirements from the substrate but other rooted types 
cannot. Maybe it takes a long time for things to reach a satisfactory 

Ok enough rambling. Bye...

Steve P in Van.