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Sand (was RE: Aquatic Plants Digest V4 #823)

"Paul Kelley, M.D." <NoleDoc at chartertn_net> wrote:

> Hello new friends,
> Just started the list and anticipate a very good experience. I've been
> reviewing and searching the archives (I believe it was this list) and wow!
> So many folks with expertise who also kindly share their wisdom... this is a
> very nice community.
> I am about to order some plants online. The place most promising so far is
> Pet Warehouse but I have no experience with them at all. Ideas?
> Alternatives?
> Also I've been thinking about adding organics to a two layer substrate. The
> bottom layer will be, one part Schultz's aquatic soil (a laterite material,
> baked clay) to roughly two parts neutral sand. This layer about 1.5 inches
> thick. Covered by regular gravel, another 1.5 inches.
> My thought is this: mix some potting soil, say three parts sand to one part
> potting soil and one part peat, and laying it on strips of cheese cloth in a
> thin layer, perhaps 1/8 inches thick.
> I would then roll the covered cheese cloth up and make tubes from 1/2 to one
> inch round. Place those in the bottom layer at regular intervals. Idea here
> is to make the nutrients available to the roots but lower the risk of
> contaminating the water column.
> I've also considered laying a strip of plastic, 1/4" gutter guard between
> the gravel and the 'substance' layer. This stuff would likely make it very
> hard for substrate shifting fish to go beneath the gravel to stir up the
> lower layer.
> So, what do you wise people think? Workable or do I need to go back to the
> books and rethink things?
> I'd be very interested in communicating with any fish person near the NE
> Tennessee area to compare LFS and share resources.
> Enough for a newby. Thanks by the way for making this a very fine list.
> Paul


Is this your first planted tank ? If so, I would strongly advise you
to stay away from complex substrates, and in particular to avoid any
fine-grained sand. Based on my own limited experience, and on what other 
people already reported. 

When first set up my first "true" planted aquarium (meaning high ligth and 
CO2 injection) I decided to make a sand-based substrate (despite contrary
advice...). It turned out to be a bad idea, now almost two years down the 
road. Sand basically prevents any significant circulation of nutrients 
between the lower substrate and the water column. At first I thought this 
would be good, since it would prevent nutrients from leaching _from_ the 
substrate _into_ the water column. But the opposite also happens: nutrients 
in the water column don't move into the substrate. So now I have 
nitrogen-hungry root feeders such as E. tenelus that must be continuously 
fed with Jobes spikes and iron tablets, at the same time I have 
nitrogen-rich water that I have to control by large water changes, lots of 
fast growing stem and floating plants, and by giving excess fish (platies) 
to the LFS. Initially the tank sustained 0-5 ppm NO3 continuously, now it 
never gets below 12-15 ppm.

But worse than that, the substrate got compacted to the point it developed 
a strong tendency to form anaerobic pockets. So now I have the added 
aggravation of having to poke/move the substrate material very frequently. 
And I don't have any organic material in there except mulm. I bet that
if you add organics at the start, the substrate will become anaerobic
sooner than mine did. Note that even if you mix fine sand with some other
coarser-grained material, the sand will soon sift to the bottom, effectively 
segregating itself into a more compact layer.

I am now convinced that for long term stability we need to provide ample 
pore space throughout all the substrate depth. Better yet, also add 
high-power (Dupla style) heating cables to force water circulation. 
My new tank is being set up in this way, (flourite/gravel/profile only,
no sand, and heater cables). and in time I'll redo the existing tank with 
the same technique. No sand anynore. This is of course my limited
experience, and some people also report that they get good results
with fine grained sand. I wonder for how long they get those results
though, and would like to hear from people that have kept sand-based
substrates for a long time, say more than 2-3 years, without facing
compaction/anoxic situations. And of course, some people like to redo
their tanks often, so long term stability is of no concern to them.

- Ivo Busko
  Baltimore, MD