# Osmocote revisited



## jetsfan (16 Oct 2011)

Bear with me please as i'm a newbie about to attempt my first aquascape.
Been looking at this forum for a while and absorbing the excellent advice.
So,have decided to go the tesco cat litter route and have bought some Osmocote to go underneath it.
Have bought all the ferts to go down the EI route as well.
Looking at recent posts tho',particularly the Miracle gro one,is there a problem with adding Osmocote to my substrate??
Seems some people are suggesting it gives a massive ammonia spike for months on end??
Have I got this right? As I said I'm new to this so now I'm really confused as I'm about to set up.
My tank is 330ltrs and I reckon 5 bags of cat litter will be right for what I'm looking for.
Think the Miracle gro prob was in a smaller tank but want to get this right from the start so,if I cant use Osmocote
what are my options?
Any help appreciated.


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## dw1305 (16 Oct 2011)

Hi all,
Osmocote is a "_controlled release fertiliser_", this means that all the nutrients it contains don't go straight into solution (like the salts used in EI would), but leak out over time. 

When salts are in solution, they are "ions", atoms or molecules that have lost or gained an electron and are "charged particles". An anion like nitrate (NO3-) has gained an electron and a cation like potassium K+ has lost an electron. 

Cat litter is a mixture of calcined clays and diatomite, and these have "cation/anion exchange capacity" CEC/AEC, the ability to hold and exchange ions.

Teh good news is that all of this means that the nutrients in the Osmocote won't be instantly available, giving you  huge spike of nutrients, but will trickle out and many of the ions will fill the exchange sites on the Cat litter.

The bad news is that Osmocote is designed for terrestrial plants and its release is quickest in warm, wet conditions and will contain ammonium nitrate (NH3NO3) as its nitrogen source.

Cat litter and Osmocote is a good mixture, but as you are going to use EI, you don't need to add very much of it to the substrate.

cheers Darrel


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## jetsfan (18 Oct 2011)

Cheers for the reply Darrel.Have you any thoughts as to how much Osmocote i should use in the substrate.
Theres so much top advice here my head is spinning as a newbie. Hope to take a few photos as i build it up anyway and post them.
Wish me luck.


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## foxfish (18 Oct 2011)

There are a few pictures on the site that show guys using osmocote, they just seem to use a very sparse covering.
In fact a covering is the wrong term - perhaps one grain for every square 50mm as I remember?
Hardly worth the effort if you use EI!
Perhaps consider some substrate fertiliser tabs from a mainstream supplier that are designed more for the purpose of fish tanks?
I used some bonsai soil under my cat litter, it said on the bag is was suitable for fish & I have suffered no ill effects but weather it made any difference I cant say as the last three or four tanks I have set up have all had good growth & they have all had different substrates sytems!


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## jetsfan (19 Oct 2011)

Thanks for the replies.Looks like I bought a box of osmocote surplus to requirements!!!
Oh well,can always use it on the veg patch next year!!
Might well try the fert tabs route as well.


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