Hi Jan How are you? Hope you are well.

I'm fine and feisty today. )

Just perused the link you supplied and this seems to be pertaining to
terrestrial crop soils which is a completely different system. I can't
comment on PH in soils as I have zero expertise in this field ;o.
However, when it comes to aquatic plants I can assure you that plants are
more than comfortable within our ph ranges, lets say between 7 and 9, is
that reasonable?

IME, most "growing above water level (non-submerged) aquatic plants, are
similar in needs to terrestrial plants, and do better in the mid-ranges of
7 to 8, with some doing fine 5 to 7.5 (think bog plants, very acidic
conditions). There are others I'm sure that can handle the upper ranges,
which I assume is in your planted aquaria? Though you do confuse me when
you say they grow well at high pH, yet your aquaria isn't running at a high
pH???

Derek mentioned, WH, and IME also, tend to go downhill when the pH is 8.5
and up.

98% of the aquatic plants in the market will do just fine at PH 7-8.5.

See, we are on the same page, only I believe one has hit the top at 8.4....
Going back to the OP problem, her test strips only test to 8.4, so we don't
have any idea how high her pH really is, just because the color is just a
hair darker/brighter, does mean it is just a hair above 8.4 (been there,
done that, and when I got the WIDE range test kit had a pH of 9.0).

Saying that plants prefer a certain ph to thrive is a complete myth, really,
I'm not being a wise ass!

It is a highly studied fact, that all plants have a pH at which they take
up the majority of needed nutrients. One could dose a plant with Ironite
say, but if the pH isn't in the range that the plant can make use of it, it
will still yellow and die. Thrive... yes, most plants can live a long time
in bad conditions, even survive, but just like koi, won't grow as big or be
as pretty in color (bloom).

To the OP Gabrielle, I still believe that its a nutrient deficiency and
probably NO3, floating plants are relying on nutrients from the water
column, I'm pretty certain that they're starving.

And I'm totally certain, it's her pH. ;o)

So from an aquatic website:
http://www.thekrib.com/Plants/Fertil...ate-kelly.html
*I quote*

* Most macronutrients (N, Ca, Mg, P, K, S) are maximally available
at a pH of 6 to 7. Most micronutrients (Fe, Mn, Zn, Cu, Co) are
more readily available at a low pH. [Note that most aquarists,
in contrast to farmers, would not consider very soluble phosphorus
to be a good thing! Also, at mid to high pH the available N is
NO3-, which is rumored NOT to be preferred by aquatic plants. The
preferred ammonium N is most available near pH=6 or below.]*

Now for happy fish, plants, and more importantly, imo, the filter bacteria,
it is good to have pH above 6.5 and below 8.5, with the optimium being
between 7 to 8.

Getting back to the OP, her pH from the tap didn't come in high, so
something in the pond is making it so, and that is what she has to figure
out and correct. It could just be a balance thing, bring the KH up high
while the pH is high, then do water changes and see if that fixes the
problem. This worked for me, I'm hoping it will work for her. ) ~ jan


~Power to the Porg, Flow On!~