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Re: Aquatic Plants Digest V2 #952

> Subject: Re: Soil substrates
> Why is a silty soil or loam of low organic content
> preferable to one of high organic content and how
> inhibiting is a good topsoil? As a general rule do
> you cut your soil with course sand or gravel?

A silty loam is also the most fertile terrestrial soil ... it has a 
fairly high capacity to hold cations, yet does not compact the way that 
clay soils do. As to why organic content should be low ... research has 
clearly indicated that as the organic content increses, growth decreases. 
The reasons are unclear but two have been put forward; high OM soils are 
less dense and therefore less fertile as there is less capacity to hold 
nutrients per given volume, and/or anaerobic processes in saturated soils of 
high OM produce lots of toxic byproducts because of the extreme reducing 
conditions. Take your pick.
Personally, I have cut my soil with sand. We have a very dense clay 
locally, however, and it really comacts so I have been thinking that the 
next time I set up a tank I will use 1 to 3 mm gravel

> My rooted plants are doing alright in a sandy topsoil;
> however, all of the stem plants remain frozen in time 
> without PMDD. This is especially true when there is
> no CO2 addition. When I use a "natural approach" as
> advocated by Dave, my stem plants don't grow. By far
> the best growth these plants have shown to date is in
> a tank with a course gravel substrate, PMDD, CO2, and
> no substrate additives save fish poop.

Not all substrates are created equally. Sand soils are poor in nutrients 
... or are you saying you have a topsoil with sand added? How much light 
do you have?

If you eschew the CO2, then you must use powerheads or airstones to 
ensure an adequate circulation of water in your tank. The Sears/Conlin 
approach is an excellent way to successfully grow aquatic plants ... I do 
advocate a 'natural approach'. However, once you have adequate lighting, 
a deep fertile substrate, excellent water movement in your tank, a 
routine of water changes and nutrient addition that controls algae... 
whew! ... and you are still not satisfied, then it is time for more 
expensive measures ... for that I refer you to George.

> - --
> Dave Whittaker
> ac554 at FreeNet_Carleton.ca

> Can anybody recommend a good book to help with snail identification?

Pennak, robert W. Freshwater Invertebrates of the United States. John 
Wiley and Sons (of course the species found in this book are strictly NA)