Possible BBA and a host of questions

Marcus_F

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I will say there is one thing which is confusing me. Nitrate, I've always been told to keep it to below 20ppm in the tank water and we should keep it low to avoid Algae yet I'm dosing the tank with Nitrate? Is it the same chemical, am I right to be adding more as part of the NPK?
 

hypnogogia

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I will say there is one thing which is confusing me. Nitrate, I've always been told to keep it to below 20ppm in the tank water and we should keep it low to avoid Algae yet I'm dosing the tank with Nitrate? Is it the same chemical, am I right to be adding more as part of the NPK?
The idea is that you dose the same (or slightly more) than the plants take up., and that with regular 50% water changes you keep it to safe levels. In a heavily planted tank, the plants are the best way to reduce nitrate.
 

dw1305

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Hi all,
I've always been told to keep it to below 20ppm in the tank water and we should keep it low to avoid Algae yet I'm dosing the tank with Nitrate? Is it the same chemical, am I right to be adding more as part of the NPK?
Have a look at <"A simple continuous......"> and <"Nitrates">.
Interestingly, no indication of magnesium
They aren't obliged to report it, because it doesn't have a regulatory limit. The same applies to phosphorus (P), no regulatory limit, so no chance of the water company having breached the regulatory limit.

There won't be much magnesium in the water <"for geological reasons">. The water report is quite interesting, it looks like a blended supply with some coming via nitrate stripper (or even possibly via desalination). The bulk of the water will come from the chalk aquifer, which accounts for the calcium and hardness values.

It is an area of England with severe water shortage issues. Cambridge gets about as much rain-fall as Jerusalem, and because southern East Anglia combines arable agriculture with a realtively dense population most of the aquifers and rivers are eutrophic.

cheers Darrel
 

Witcher

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I've always been told to keep it to below 20ppm in the tank water and we should keep it low to avoid Algae yet I'm dosing the tank with Nitrate?
I think that one of the biggest problem among plant keepers is that they quite often tell you definite values: "You must keep your nitrates below 20ppm", "You can't use more than 2ppm PO4", "You must keep your co2 at 30ppm" etc etc. Thing is that every single planted tank is completely different from each other and levels of nutrients should be set according to what you have in your tank - plant mass, alkalinity, demands of particular plants for particular nutrients, light and other things.

As an example: I keep my tank (or tanks) with rather big plant mass - approx 70-80% of the tank volume, after massive trim it still looks like it's filled to approx 50%. I don't supply CO2 (only via glut/organic acids), but have strong light - just like in typical high tech. By simply testing I know that 7-9ppm of NO3 weekly is about perfect for typically green plants when my tank is full to the level when I can't even see some of them, completely obstructed by others (for example I only know that I have bolbitis, but very rarely see it). Now - what would happen if I'd introduce constant supply of CO2 at let's say 30ppm? Demand for NO3 (and other nutrients) would increase dramatically and I doubt if 30ppm of NO3 would be enough to not see any N deficiencies in few days - and very likely many of the plants will be covered with hair algae. So that's it - you can use what other people say as a rough guideline but in the end levels of nutrients in your tank will be completely different because of completely different conditions.
 

jaypeecee

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It is an area of England with severe water shortage issues. Cambridge gets about as much rain-fall as Jerusalem, and because southern East Anglia combines arable agriculture with a realtively dense population most of the aquifers and rivers are eutrophic.
Very interesting.

JPC
 

jaypeecee

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Hi @dw1305
That is correct, but only relevant if you can get the concentration below two micro-molar orthosilicic acid in solution, one you are below that level it will begin to limit diatom abundance.
So, that's about 0.2 ppm, if my calculation is correct. I think it may be possible to get below this figure and I believe I have an article discussing this. Will try to find it.

JPC
 

jaypeecee

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dw1305

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Hi all,
It is an interesting article and certainly has some suggestions that ammonia favours the growth of cyanobacteria over diatoms.

Probably the most relevant bit to this discussion is:
Use of sodium nitrate and sodium silicate fertilizers at a 1:1 nitrogen:silicon ratio .........and containing 0.21 mg/L silica was shown to be quite effective in increasing both the abundance of diatoms and their proportion of the total phytoplankton. Of course, in this situation, the concentration of silica was very low – normal seawater contains 6.4 mg/L silica. Diatoms grow quite well at the silica concentration in seawater, and it is not known how low the silica concentration must fall before diatom growth is negatively affected.
The real problem is that the the author has to use the SiO2 content of the water as a proxy for the orthosilicic acid (H4SiO4) content, without knowing the empirical relationship between the conversion of SiO2 to H4SiO4.
........For example, silicon dioxide reacts in water to form silicic acid, a weak acid that is largely un-ionized within the pH range of most natural waters. When calcium silicate reacts with carbon dioxide in water, the resulting dissolved substances are calcium ions, bicarbonate ions (alkalinity) and silicic acid. .................Silicon concentrations in natural waters typically are reported in terms of SiO2 and usually range from 5 to 25 mg/L in freshwater bodies..... A silica concentration can be converted to silicon concentration by multiplying by the factor 0.467, the proportion of silicon in SiO2.
Because diatoms are pretty <"much universal in liquid water"> they have to be incredibly efficient silicon uptake.
..........Diatoms are ubiquitous in both marine and freshwater environments, contributing up to 25% of the world's primary productivity and forming the basis of many aquatic food webs......
cheers Darrel
 
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Marcus_F

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Could high Nitrates be a cause of Diatoms which won't go away then?

I haven't tested my tanks Nitrate in a while because this place suggested the inaccuracy of the results. I guess it's better than nothing and to be fair as with any test you do in the world, even if it's inaccurate numbers, as long as it's consistently inaccurate you can monitor for increases or decreases. It's the same with car tyres, a long of pressure readers will give different values but if you use the same one, it's all relative to your original and first control test. If that you follow me :)

Of course random fluctuations caused by a bad test would be troublesome for my theory.
 

dw1305

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Hi all,
Could high Nitrates be a cause of Diatoms which won't go away then?
It is back to the <"ubiquity of diatoms">, there is an enormous assemblage of species that changes along environmental gradients.

Have a look at the <"Lenntech page on eutrophication">, which shows how the cyanobacterial and algal assemblages are affected by elevated levels of nitrogen and phosphorus. I don't look on <"algae and plants as really any different">.

Because diatoms have a persistent "skeleton" (frustule) they can be used in <"biotic indices">. Their persistence allows them to both indicate present, and former, conditions by differences in their relative abundance in the water column and the sediment.

cheers Darrel
 

Nick72

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Hi all, It is back to the <"ubiquity of diatoms">, there is an enormous assemblage of species that changes along environmental gradients.

Have a look at the <"Lenntech page on eutrophication">, which shows how the cyanobacterial and algal assemblages are affected by elevated levels of nitrogen and phosphorus. I don't look on <"algae and plants as really any different">.

Because diatoms have a persistent "skeleton" (frustule) they can be used in <"biotic indices">. Their persistence allows them to both indicate present, and former, conditions by differences in their relative abundance in the water column and the sediment.

cheers Darrel

Err.. So was that yes or no then?
 

dw1305

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Hi all,
impede Cyanobacteria. Any truth in that one as far as you know?
I've never really suffered from them and I will have low NO3 values in the tanks. I would say I'm sceptical, but I don't have any practical experience. As with diatoms there are different cyanobacterial assemblages that are adapted to oligotrophic and eutrophic conditions.

I think one reason why this might be true, for some species, is they are nitrogen fixing or "diazotropic", so may be at a competitive advantage when NO3 levels are low.

Have a look at @jaypeecee thread <"on the cyanobacteria in his aquarium">. He identified Oscillatoria spp,. which are both <"non-diazotropic".> and associated with <"high nutrient levels">.

cheers Darrel
 

jaypeecee

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Hi Folks,
This is the article I had in mind but I was mistaken in thinking that it advised on silicate reduction.
Perhaps this is what I'd remembered:

"There is evidence that nitrogen:silicon ratios above 3:1 lessen the growth rate of diatoms".

JPC
 

jaypeecee

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Hi @Marcus_F
I haven't tested my tanks Nitrate in a while because this place suggested the inaccuracy of the results.
The major unknown for me with nitrate test kits (and, perhaps, others) is the extent to which other ions in the aquarium water interfere with the test method. There are very few resources available on the accuracy of test kits. The one below is one I discovered a while ago:

https://www.researchgate.net/public..._ASSESSING_THE_RELIABILITY_OF_WATER-TEST_KITS

JPC
 

dw1305

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Hi all,
Perhaps this is what I'd remembered:

"There is evidence that nitrogen:silicon ratios above 3:1 lessen the growth rate of diatoms".
I think that was a competition effect, because the diatoms were then out-competed by cyanobacteria and green algae, so it is really out of the frying pan and into the fire.

In terms of lakes, low nutrient ("oligotrophic") lakes have much less phytoplankton biomass, but a higher proportion of diatoms within that assemblage.

cheers Darrel
 

jaypeecee

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Hi Folks,

And, the above report uses almost exclusively test strips. Say no more! (As Eric Idle* would have said)! :)

@Marcus_F ---- FYI, I use the JBL Nitrate Test (liquid reagents)

* Monty Python sketch

JPC
 
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