Nick L-S wrote in message ...
Hi All,

I recently went out and got a 2ft 36W compact fluro, because my plants
were dying horribly. I have a community tropical tank, but i like real
plants. Plants we have had in the past have just slowly withered and
died. The new light appears to be doing quite well, but the tank has an
undergravel filter, which i hear isnt good for plants.

My question is, does pH matter? The water here has a naturally high pH,
but if i try and use pH-down (for the fishes) it just goes back up again
in a matter of days. I dont quite know why, but are there any plants
which dislike a high pH?

Well it's a TWO part issue when you talk about pH. Plant like good CO2
levels.
CO2 and KH TOGETHER determine the pH. CO2 is the acid and the KH is
the buffer.

Plants want CO2, not some specific pH or KH.

Take a look here under "references" for the pH/KH/CO2 table.

You'll note that at a KH of 3 and a pH of 6.4 will give you 35ppm or
mg/l of CO2. Now look at KH of 20 and a pH of 7.2. This will give you
a CO2 level of 37ppm about the same as the KH of 3.

All you do to get a good CO2 level is add enough CO2 gas to drop the
pH to 6.4 for the KH of 3. That's it. Don't use anything else to
manipulate the pH. Just CO2 gas since this is what the plant want.
You do not want to have less than a KH of 3 generally.

So make sure you understand the relationship, it takes two to tango
here.
One by itself does not tell enough information about CO2 levels.

All the plants seem to be doing OK except for some long and dwarf
pongol, do these plants need special treatment? Im currently not using
any sort of fertilizer, but i am thinking i will....
cheers!
nick

Terrestrial plant, I have it along my sidewalk here.
Generally if you add a fair amount of light, you'll need more CO2 and
nutrients. These are the three things plants need to grow well(Light,
CO2 and nutrients). If one of these is out of balance, then you get
algae generally.
Regards,
Tom Barr