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Discussion Starter · #1 ·
Hi, I'm new here but I've always read about low stable NO3 making red plants red and high PO4 keeping spot algae from growing on the glass. Has anyone maintained a NO3 value of <5mg/l and a PO4 value of 1.5-2.0 mg/l? This is way out of the 10:1 ratio which I've read about though. I want to make my red plants redder and at the same time try to remove the spot algae from my anubias and from the glass. Thanks in advance for any advice :)
 

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Use less light, this will make it easier to maintain low N.
A redder plant is a stressed plant, go too low and you will stunt your plants.

Adding light bulbs that make the reds appear redder to you also may help.

Regards,
Tom Barr
 

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plantbrain said:
Adding light bulbs that make the reds appear redder to you also may help.
I just got my GE9325ks today and the difference in color of the L Glandulosa under them and under 6700ks is striking. In the 6700k they appear more brownish red than red, under the 9325ks the color needs to be seen to be believed, really neat.
 

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Funny you should mention the GE9325's. I, too, put them in just the other day and was immediately impressed.
I was expecting a whiter, bluer light but they're warmer with very good color rendering. And what they do for reds is remarkable.
I can't speak to their effect on plant growth. I use MH's as my grow lights but, for general tank illumination in a T12 flourescent, they're the best I've seen.

Bob Vivian
 

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I am not sure that keeping NO3 at 5ppm will do it as far as making plants redder. The ratio of N to P isn't so important. The question to ask is, will the plants actually be nitrogen deficient at a NO3 level of 5ppm. I suspect not. I got some nice red plants back in August in a tank where the NO3 level was not measurable. I got some Hygrophila polysperma to produce a nice pink-red color and some Blyxa japonica also to turn pretty much red, with red striping on the leaves and pale green inbetween. The plants were still growing, but not as fast as they could. Interestingly, the plant that suffered with actual N deficiency and die-back of some of the older leaves was Zosterella dubia. Plants experience low nitrogen levels frequently in Nature, and are not harmed much, unless the deficiency is really extreme.
 

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The ratio of N to P isn't so important.
My observations contradict this statement. Formerly, I was never able to get Ludwigia arcuata past a dull orange, but now I can (consistently) get reds out of this and other plants by raising the P to N ratio. You can have blood red plants up to even 10 ppm NO3 if you keep PO4 at 1.5-2ppm.

Outright stressing the plants with both lean P and N just resulted in dull, slow growing plants. I observed high growth rates and excellent health, however, with high P to N.

Carlos
 

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I don't think my plants (the Hygrophila and Blyxa) were stressed by lack of P, but I know that they were N deficient.
 

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I've been curious for a while about nutrient levels and deficiencies and I had this thought:

Isn't it logical to assume that if any nutrient is measurable in the water column than by definition there is no deficiency?

I mean if there is even 2mg/l of NO3 in the water column that means the plants still have that much available to them before there is no more?

Or is it that plants have problems using nutrients if they are *below* certain concentrations in the water column? :? But on the other hand I know that if I don't dose NO3 it will get to zero.... same with Fe... So therefore plants can either assimilate the nutrients all the way down to 0 concentrations or they are precipitating out of solution.
 

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Discussion Starter · #10 ·
The reason I’m asking because through my observation on my rotala rotundifolia, this plant turned really red at a very low to undetectable NO3 values (<5mg/l) the last I checked with my SERA NO3 tester. Then, the red colour diminishes as I add KNO3 to about 5mg/l. I noticed this from their growth tips. PO4 was maintained at 1.0mg/l. I’m using two 7500K 38W FL lights, one 6000K 30W and one 3000K 30W warm white just above my red plants to try and get them to look red in my 4 feet 220 litres tank. From this observation alone I can say that low NO3 do bring out the reds, but how low is low? My question is, how long can I maintain low NO3 (<5mg/l) before I actually start to stunt the plants?
 
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