Re: dead tree leaves in aquariums

> From: George Booth <booth at hpmtlgb1_lvld.hp.com>
> > From: stevensj at calshp_cals.wisc.edu
> > 
> > I imagine that using dead leaves might be no less convenient than peat,
> > but they may make a better substrate which doesn't float around the tank
> > & get in your filters like peat does.
> What do people think about the appearance of such a substrate?
> Natural looking, of course, but *too* natural?  I like a certain
> amount of artificial neatness in the aquarium.  

I think leaves would inhibit circulation in the substrate and if
buried, contribute to anaerobic decay conditions. Decaying material
in the substrate greatly increases the oxygen requirements of the
substrate and drastically alters its chemical and biological
composition. As George pointed out in the rather long article he
forwarded to me, an aquarium cannot approximate natural conditions
since in streams, there is a flow gradient in the soil. In stagnant
ponds, I suspect anaerobic conditions frequently do occur and *some*
fish and plants may be adapted for these conditions. Also remember
that ponds also undergo seasonal flooding in many locales and
water table fluctuations which can induce nutrient infusion. These
nutrients remain due to the extremely high CEC of those pond 
bottoms. You should remember that the CEC of granular laterite is
not high but much higher than sand or gravel which has virtually
zero CEC. Mud has a pretty high CEC on the other hand. Back to the
point, even with the small amount of circulation induced by
heating cables or slow RUGF and the strong flows we might induce
in the tank by using power heads, we can ill afford to compromise
that circulation. That is the point of having the top layer of
the substrate fine gravel; there are lots of spaces for flow to
occur. My feeling is that when we build a layered substrate with
vermiculite, dirt, humus or fine lateritic clay (not the granular
stuff) and then cover it with another layer of coarser particles
that there is a zone here where root activity is optimal. In fact
we are giving the plants a bit of choice as to which conditions
they might favour for their rootlets. George, even with the
laterite granules, don't they recommend a layered approach? When I
looked at T.O.A. pictures in the early days of laterite, it sure
looked like they were using a very clay-like mud, red in appearance.

Another observation from nature: there are several topological
formations which produce alkaline ponds. There is no water table
flow here; it lies over an impermiable layer, (rock or clay) and
just evaporates as time goes by. Very little grows there. I think
sedge grass is about the last thing before it goes completely
lifeless. Anybody else have any comments about alkaline and/or
anaerobic aquatic plant habitats?