>From: Eric Schoville <schovill at expert_cc.purdue.edu>
>Which type of sand should I use for my aquarium.  There are three
>types that I know of, Silica sand, Crushed coral or beach sand, and
>the Play sand that they sell at hardware stores.  Alternatively I could
>collect some form a local creek.  
>Also, which fertilizers should I use in the substrate.  Is there an 
>inexpensive source for Laterite, or do people recommend that I put
>a layer of potting soil beneath the sand.


IMO, there is no "right" answer for either of these questions.

Most modern hobbyist books recommend gravel that is 2-3 mm in size
(about 1/8").  The reasoning is that finer substrate (say sand) will
compact down, making it difficult for plant roots to penetrate, and
also making it difficult to keep the soil aerated so you don't get any
dead spots.  Use larger-sized gravel, the books say, and the plant
won't be able to anchor itself well.

But there are people who use fine sand, and people who use larger
gravel.  Neil Frank wrote recently in The Aquatic Gardener that Amano
(who wrote the book "Nature Aquarium World") uses larger gravel.

I was talking to Diana Walstad (technical editor of the Aquatic
Gardener) and she told me that the people in academia almost
exclusively use soil to grow their plants. Diana is the only person I
know who reads academic publications, and I believe her information is

As far as substrate additives are concerned, there is also quite a
diverse range of opinions among people who are quite successful at
growing plants.  Potting soil, cow manure, garden soil, laterite or
baked clay, everything has its advocates.  Neil Frank recently posted
comparisons of different substrate materials, and as you would guess,
they vary widely in nutrient content and other properties.

If you want a system that can be counted on, personal opinion is that
the Dupla approach is the best bet.  But in my experience, and that of
others who used Dupla laterite and gravel without substrate heating or
UGFs, the tank produces good results for about a year, and then begins
to deteriorate.

Unfortunately, there is no inexpensive commercial source for laterite.
Aquarium Pharmaceuticals used to sell laterite, but it seems to be no
longer available, so Dupla is the only source.