# What ferts to use for inert, high CEC substrate?



## CatG (Apr 10, 2010)

I've been looking around, but can't seem to find a definitive answer. I want to use haydite, a supposedly inert, high CEC material (fired shale) as a substrate. I would like to do as little water column dosing as possible, so I was hoping I could add ferts to the bottom layer of the substrate, and then cap it with the haydite. Can I crush up root tabs and dust the bottom of the tank with that? Should I use individual ingredients instead (like laterite, dolomite, etc)?

Any help would be greatly appreciated, as I seem to be running around in circles and am starting to feel very overwhelmed and discouraged.

Cat

Ps. From what I gather, haydite is not used alot, so any advice regarding how you fertilize a substrate with similar properties would be great.


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## Michael (Jul 20, 2010)

The usual way this is done is by putting a soil layer under the inert cap, as in the Walstad method. The mineralized topsoil posts in the library have lots of information on this.

Some people have used Osmocote, a slow-relase fertilizer made for terrestrial plants. The problem with Osmocote is that no one really knows how much is safe to use, or how long it lasts.


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## CatG (Apr 10, 2010)

Thanks for the info about the osmocote. I will look that up and see what I can find. As for the topsoil, I have that in another tank, and would like to go a different route with this one if possible. I don't like the muddy mess it makes when I have to uproot plants.

Cat


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## Left C (Jun 14, 2005)

I use the "Plus" version of Osmocote. It contains NPK and traces. Regular Osmocote contains only NPK and a large portion of the N is in the form of urea and ammonium which may cause problems.

Below is a picture of Osmocote Plus.


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