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Re: APD, nutrient method

Jeff Kropp jjke at pacbell_net wrote:
> You mention desired calcium concentrations of 30ppm in your post. As I
> recall Dave Huebert was saying 20ppm was more than enough and 2ppm was
> about what was needed for aquatic plants. Can I assume your experience 
> has proved 30ppm necessary?

Quite the contrary. The concentrations are not critical at all; they are
only designed to be sufficient to ensure adequate nutrients. 30 ppm is a
rough approximation of the concentration you get using 1 tsp of calcium
carbonate per ten gallons of water and that's the only significance to
the value. I found that under initial conditions with peat, this was
being absorbed by the peat so I double the amount. The range of
tolerable calcium concentrations is one of the widest!

> By the way thanks for your post, I may try it when I reset-up to 
> rectify the 140ppm of calcium leaching from beach gravel.

That's not too much calcium; many plants will thrive in hard water like
that. The problem with using a continuous source of calcium in a tank
with large sources of humic acid is that you're probably not going to
know your actual concentrations very well. That doesn't mean it won't
work however!