Desired levels of various elements

I'm having a problem with high levels of phosphates in all my tanks, and my 
50gal chiclid tank which has no plants, also has elevated levels of nitrates. 
Phosphates combined with nitrates...guess what. Yep I've got an algae bloom. 
It's diatoms specifically. brownish red dusting all over the glass, heater, 
gravel, etc.. Low lighting may also be playing a part in it, but the phosphate 
is in excess of 10ppm and the nitrate is around 35ppm. Prior to this outbreak, I 
recently did a delicate all day shifting of the entire contents of a 20gal with 
fish, gravel, etc., to a new 50gal tank and hood. I'm thinking that because I 
had to add a lot more fresh water than I would have during a regular water 
change, plus adding more new gravel to the old, perhaps the bacteria colonies 
were more severely smitten than I figured they'd be, and now I'm getting some 
spikes on these elements a little like cycling all over again.

Here's the question that qualifies this message in the plants mail list. What 
exactly are the optimum levels desired in planted tanks for phosphate, nitrates, 
and iron? Recall that I'm having phosphate levels in my 75g and 50g planted 
tanks as well. The books I have and the test kit instructions don't come out and 
say for example, phosphate level should be 0ppm or 5ppm. Same thing with the 
iron. I'm pretty sure nitrates should be kept as close to 0 as possible.

I don't think you want 0 phosphates as plants need a small amount to aid in 
photosynthesis don't they? If they get too much then they become damaged and 
algae grows better right? I have a lot of algae right now, and I didn't know I 
had phosphates til I got the test kit today.

Thanks for any advise.

Douglas Duncan
email: duncand at sprynet_com
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