Re: Soils & Lights

George wrote:
> > Roni Talukdar wrote:
> > 
> > I'm setting up my 100 gallon for plants in the near future and with
> > the recent posts on soils as a substrate, I was wondering what you think
> > about my proposed substrate
> > 
> >         Small (1/2 inch) layer of gravel
> >         1-1 1/2 inch layer of laterite mixed with vermiculite
> >         1 1/2 inch layer of earthworm castings
> >         1 1/2 inch layer of gravel
> Given that good growth is easily obtainable with laterite OR
> vermiculite OR earthworm castings OR soil, I think you have gone a bit
> overboard in trying to provide a "rich" substrate. 

There are two reasons for using a layered approach in soil substrates:
1) to have a layer of sand or fine gravel on top to prevent fish
from disturbing the soil and creating turbidity
2) to create a lower layer of reduced oxygen content (anaerobic) with
an overlying layer of oxygen rich substrate (aerobic). See previous
posting on anaerobic discussion with Dr dave and myself.

To anyone wishing to try out soil substrates and not wishing to get
into the technical aspects, you should stick with the Jim Kelly
recipe (email me if you don't get TAG) or others described in TAG
which have been field tested. A potential problem with a lot of
soil in a substrate is you might have too much growth!! :-0
I'm curious to hear Paul Krombholz's comments when he gets time.
I think he uses a higher ratio of soil and no solid fertilizer and
no vermiculite but I haven't found his recipe in my saved files. 
He has said 1/3 manure & 2/3 soil composted aerobically for a 
few weeks but I don't know if that's mixed with gravel in the 
aquarium. Possibly he puts that in the bottom with a layer of 
gravel on top. I suspect 1/3 manure may be above the optimal
organic content but apparently such substrates are possible with
no harm to fishes or plants. Paul told of a story of a aquarist
using 1/3 raw sheep manure, 1/3 raw bovine manure and 1/3 soil.
An echinodorus plant flourished for several months before it
turned anaerobic.

To critique the above I'd suggest that the bottom layer of gravel
won't be necessary. I'd put laterite powder on the bottom and mix
the vermiculite with the soil. Cover with sand or gravel. The tank I
have soil in has rather a lot more vermiculite and gravel than soil.
I plan to test something a little more experimental next time I 
tear down or if I just get bored with my gravel tank.

> Also, the careful layering that you describe will soon be homogenous
> as you plant and replant (a plant tank with optimal growth will
> require serious pruning and replanting about every two weeks).  As
> some of the components get to the top of the substrate, you may find
> that they will cloud the water or begin to get unsightly. 

I wouldn't uproot plants in a soil tank frequently for that reason but
you can do it if you really want the roots and all. Frequently I pinch
off stem plants at the base rather than uprooting. Most grow back.
H. difformis is rather like a weed and the only way to get rid of it
seems to be to uproot. If it gets overshadowed by taller plants however,
it looses the competitive edge. Vermiculite doesn't create a problem
with cloudiness. Soil from an uprooting settles after a few hours.
A lot of soil on the surface might be a problem with Corys. The 
substrate won't get homogenous however, without quite a lot of stirring
IMHO. ;-)

> I think you would be better off to make a simpler substrate and apply
> more effort to other things such as water circulation and fertilizing.

Two important factors along with regular water changes. A little soil
is very beneficial to certain plants IMHO. From my limited exchanges
with the lurkers on this list, I suspect there are a lot of folk out
there with lots of different combinations including heating pads
under the tanks and various substrate concoctions. They just don't
tell us about it. Some of it works, some of it doesn't.

Steve                               Vancouver BC CANADA