Re: phosphate & nitrate levels

> From: alan at peewee_chinalake.navy.mil (Alan Van nevel)
> Date: Thu, 31 Oct 1996 09:27:45 -0700
> Subject: Water company tests
> I just called my water company, to see if they could tell me the levels of
> nitrate and phosphate in my water.  The nitrates , so they say, average at
> 6.5ppm.  What levels would be considered high?

Your tank can tolerate pretty high levels of nitrate without serious effects
upon fish or plants. My test kit suggest that side effects on fish may begin
at 50 ppm. Levels above 10 ppm are probably of little use to plants and that
is the concentration which is the target for PMDD nitrate supplementation.
Your tap water is a good source of nitrate!

>  My tetra test kit doesnt register any nitrate, always at the lowest
> color scale, for my tank water (including the large tank that is still
> breaking in and is battling blue green algae.)

It's probable that your plants are nitrogen limited. If you had no fish
you could use ammonium nitrate or even urea. With fish, you can use potassium 

> But as for phosphate, [sip] what levels would be considered high?

You can expect varying degrees of algae problems when phosphates become
measurable i.e. +.25 ppm. This will vary according to the intensity of
your light. You should definitely consider levels of 1 ppm a problem but
you will probably find an algae bloom follows shortly. Strong lighting 
may cause green algae blooms at low phosphate concentration. Humic acids 
or organic acids may tend to inhibit algae growth (and inhibit the plants 
too). Something to remember, once you have green water, you won't be
able to measure much phosphate since it is being rapidly absorbed by
the algae. If you have a diatom filter, you can easily remove the green
algae and the captured phosphate at the same time. I've had good
results doing this only when the filter is properly installed and 
_sealed_. Increasing levels of phosphate indicate:
1) ratio of fish to plants too high -or-
2) frequency of water changes not enough