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Re: buffering in onyx

> I like the looks and texture of onyx sand, I've done 2 tanks now, a 20 with 3
> bags and a 38 with 4 bags.  It's so easy to work with and holds plants real
> well, I guess something that seems so good, I should be real happy.  The
> buffering is my only complaint, the description says a slight buffering
> effect, I test my Kh at 6, and my Gh at 10 in a non onyx tank.  With the onyx
> it has a Kh of 8 and a Gh of 13.  Way more than I expected, my plants don't
> like it either.  So, how long will the buffering last?  What does 'over time'
> mean?  6 months, a year or 2?  I've got 5 more bags on the floor ready to redo
> my 55g tank, now I'm not sure.
> Matt

I know the plants don't care about a KH difference of 2 from 6 to 8 and also
a GH difference of 3 from 10 to 13. If plants where that sensitive, we'd
have a lot more problems. My KH is 8 my GH is 24. _My_ plants like it.

New substrates take time to get established and matured. That is often what
folks see. Lighting, some nutrients folks can see a difference relatively
fast(3-4 weeks or so), substrates need to be looked at on a longer time
frame/scale(6 months-1 year). Even if you've taken a long time frame, also
consider how much of the blame you can put on the substrate on the CO2,
lighting or the nutrients. Sometimes just moving plants too much and not
having enough plants etc is enough to cause problems.

For folks with a KH of less than than 3 this is very good and reduces the
need to add baking soda and GH.

You may also mix the bottom layer with ground peat moss. Two handfuls on the
bottom 1/2" along with lots of mulm from another established tank mixed in
will help a great deal and should counter act a fair amount of the
Tom Barr