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Re: hard water plants

Chris Bostick wrote:

> I've got good light, CO2, have N, I assume I have P, and I dose K daily and
> also dose a bit of Mg just in case.


With very hard water it may not be reasonable to assume that you have

Phosphate can very quickly fall out of solution in hard water.  As Tom
pointed out there aren't any commonly diagnostic symptoms for a shortage
of phosphorus; it just acts like a generic "nutrient problem".  A
phosphate shortage is especially likely if you're already fertilizing
with other macronutrients.

To make problems worse, inexpensive phosphate test kits (and even
expensive ones) can misbehave badly.  All-in-all, the best way to test
for a phosphate shortage might be to add some and see what happens. 
When I first fertilized with phosphate the difference was evident in

The only aquarium fertilizer I know of that provides phosphate is
Hagen's PlantGro, which is widely available but not cheap.  You can also
use phosphate buffers, but they are concentrated enough that small
slip-ups can become big overdoses.  Jobes plant spikes also provide
phosphate, and you can use those to treat specific plants.  The reaction
from plant spikes isn't usually immediate.

Roger Miller