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Re: Aquatic Plants Digest V2 #1161


> Could some explain the basic point of using kitty litter?
> It's cheaper? Lighter? Better for plants in some way? 
> The thought of cloudiness, floating junk, and chemical
> impurities always dissuades me.
> - -- 
> Cliff Lundberg ~ San Francisco ~ cliff at noevalley_com

I'm not sure on all the history here, but I think that we use kitty 
litter because Dan Quackenbush recommended it as an inexpensive 
alternative to laterite.  Some of use tried it and liked it.  As I 
recall, Dan didn't just use kitty litter in the substrate, he also put 
Osmocote in there too.

Kitty litter is made from clay, but I think it may be baked (calcined) 
rather than clay in its natural form.  As long as that treatment doesn't 
seriously alter the properties of the clay, then it *should* provide a 
substrate with a higher cation exchange capacity and higher adsorption 
capacity.  Both of those properties improve the ability of a soil to hold 
nutrients and make them available to rooted plants.  Just how good it is 
will depend on exactly which clay was used to make the litter.

The type made from bentonite (the type that started this thread) may not 
be the best choice because of its ability to expand into an sticky 
impermeable mess, but it would provide a very high exchange capacity.
It probably could be used in small quantities.

Aside from that, I think that the presence of fine grained material 
(like clay) in the substrate will encourage plants to develop more root 
hairs, which should be good for the plant.  This might be a direct 
effect, or it could be an indirect effect because the fine grained stuff 
restricts water movement in the substrate and promotes anaerobic 
conditions.  Root hair development would then be a response to the 
anaerobic conditions.

I mixed kitty litter in the bottom 1/3 of the substrate in one tank,
potted a plant with kitty litter mixed in the bottom of the pot, and added
it to the substrate below some needy plants in an established tank.  I
didn't have trouble with clouding or floating debri in any case.  As
far as chemical impurities go...  Don't work with used kitty litter! 

Roger Miller

In Albuquerque, where there's snow on the high desert and we're waiting 
for the days to get longer.