# When is the best time to dose ferts?



## happi (Dec 18, 2009)

fertilizer stay in the water until plant start consuming it.


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## ReefkprZ (Aug 21, 2010)

happi said:


> fertilizer stay in the water until plant start consuming it.


 I wouldnt be so sure about that. there are a million little chemicle reactions going on all the time. sure most of the ferts do stay in the water untill they get used. BUT if you have any sort of anaerobic activity in your tank your nitrogen levels can reduce over a nightime period, iron can be removed by filtration (carbon etc), ammonia can offgass, algae that can photosynthesize way below the levels of plants (like bga) can consume phosphates (and other nutrients) just from ambient room light.

ok that said, most likely its not going to be a signifigant amount, but I personally add fertz first thing in the morning, either just before lights on, or just after they come on, just to give my plants a whole day to interact with the fertz. if your doing something like EI dosing this probably isnt worth doing as your ODing fertilizer intentionally anyway. but if your doing a more minimalist fert dosing regiment there could be a slight advantage to doing it during the morning before photosynthesis begins.


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## HouseofZoo (Sep 12, 2010)

I don't quite remember where I read it at, but I read it's best to dose before lights on in the morning so the nutrients are "fresh" in the water column and ready to be used by the plants. It did also state that as a last resort, right before bed should be ok too, just not as ideal. 

Like I said, I don't know where I read it, but I believe it was when I was ready about PPS-Pro.


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## plantbrain (Dec 15, 2003)

Time of day does not matter, just the lights and CO2.
In the research, there's little evidence since the total nutrient content(other than Carbon) is so small relative to the energy demand for the entire plant.

So yes, it takes more energy to take in Fe DTPA vs say Fe gulconate, but the amount is tiny, so the effect is insignificant. The total exposure time is much higher though with DTPA..........


Same deal with non limiting ferts.........exposure, and concentration are both much longer and easier for the plant to take up. You gain nothing algae wise, because they are not limited at lean or rich ppm's for plants.

So if less energy to take up nutrients is some "philosophy" you wanna pursue, you'd do best to add non limiting ferts since this places the least amount of energy on the plant. This is reflected in better growth and biomass increase, nutrient concentration in the plant.

Plenty of research shows this and goes back to Liebig's law on the Minimum, basic stuff. Concentration drives uptake of nutrients up to the non limiting point. Day night really does not matter in those cases. And if you want to maxmize it, you should not limit it to begin with, sort of contradicts the original premise:wink:

You cannot have that both ways:icon_idea
Dose = exposure(Time) X concentration(ppm)


Regards, 
Tom Barr


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## zeldar (Jun 24, 2009)

Thanks for the responses guys! Tom, you are the master, but I think I understood about every third word. haha Wayyyy over my head.

I just use the recommended dosing pattern from Seachem/Pfertz. I usually dose Pfertz micro every day, 1 squirt. Then ~1mL of N,P,K (Seachem) every other day. 

I do have a problem with BBA in both of the higher light tanks. Should I change my dosing pattern? I always heard BBA becomes a problem when CO2 fluctuates but the tanks are on pressurized co2 running 2 bubbles per second in a 10gallon tank. Both tanks also get quite a bit of water movement so I'm not to sure what my problem is. Also in the highest light tank, I get green dust algae on the glass like crazy. I have to clean the glass about every 2 weeks. I know if you just leave it alone for a couple of months it will die off for good but I just can't bear for my glass to be green for that long lol.


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## ReefkprZ (Aug 21, 2010)

plantbrain said:


> Time of day does not matter, just the lights and CO2.
> 
> 
> 
> ...


 so your saying that plants uptake nutrients 24/7 even when they are not utilizing them?


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## plantbrain (Dec 15, 2003)

zeldar said:


> Thanks for the responses guys! Tom, you are the master, but I think I understood about every third word. haha Wayyyy over my head.
> 
> I just use the recommended dosing pattern from Seachem/Pfertz. I usually dose Pfertz micro every day, 1 squirt. Then ~1mL of N,P,K (Seachem) every other day.
> 
> I do have a problem with BBA in both of the higher light tanks. Should I change my dosing pattern? I always heard BBA becomes a problem when CO2 fluctuates but the tanks are on pressurized co2 running 2 bubbles per second in a 10gallon tank. Both tanks also get quite a bit of water movement so I'm not to sure what my problem is. Also in the highest light tank, I get green dust algae on the glass like crazy. I have to clean the glass about every 2 weeks. I know if you just leave it alone for a couple of months it will die off for good but I just can't bear for my glass to be green for that long lol.


You have a too much light and not enough CO2 problem, not a nutrient issue.

All growth starts with light.
Less light= less growth
Less light= less CO2 demand= less nutrient demand= easier to manage.

Most folks start off with too much light.
Focus there 1st, then move to careful slow adjustment of CO2, never rush with CO2, good way to kill and gas fish.

Then lastly....nutrients are fairly easy.

Regards, 
Tom Barr


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## plantbrain (Dec 15, 2003)

ReefkprZ said:


> so your saying that plants uptake nutrients 24/7 even when they are not utilizing them?


They are always utilizing them. Even if they are not growing by adding carbon which is done mostly during the day, but at night they certainly do and can use those reduced carbon structures to make things like enzymes and incorporate into more complex structures, this process is hardly instantaneous. Respiration is awlays occuring so the plants are using the excess carbon they made during the day. So they can easily take up the other nutrients other than carbon to build and make structures.

Plants cannot afford to be too picky since many times in natural systems, these might be available only rarely. So there's little evolutionary rational to only take the nutrients up only during the day. 

They might take up more than they "need" also..........but.......over an entire season in a natural system, they very well might use them when the nutrients might no longer be present and they might not be so called "luxury consumption". I do not think they do luxury consumption, rather, the studies did not look at the entire season(eg Gerloff 1966 only considered a few weeks of vegetative growth, not floral or any other stages on plant growth or development).

In our tanks, I do not think any of this matters.
To date, no one has demonstrated that it does either:hihi:

Limitations, but then there is dependency on limitation and it is no longer an issue of the timing of the dose or it's efficacy of uptake. 

The fact of the matter for all uptake, which is done through enzymes........the higher the concentration, the easier it is and the faster the uptake is for the plant.

Enzyme kinetics cannot be avoided or ignored.
http://en.wikipedia.org/wiki/File:Michaelis-Menten_saturation_curve_of_an_enzyme_reaction.svg

This is also the same graph we get for light and CO2 and also.....for nutrients.










Once you get around 90% the max growth rate and above, this is called non limiting critical point. Now you have nutrient independence.
Then you can test say light and/or CO2.

If you limit nutrients, then the trade off is less efficient use of light and CO2:icon_idea If you reduce the light intensity, then the light use efficiency goes way up.........CO2/nutrients are much easier to manage.
So once nutrients become limiting... you cannot say whether it is the timing of the dose....day or night.....vs the limitation. You cannot which is doing what. It becomes hard to isolate as well as less practical from a management perspective.

Tropica did a nice study using non limiting nutrients (thus where independent) to test and look at light and CO2 in this context.

http://www.tropica.com/advising/technical-articles/biology-of-aquatic-plants/co2-and-light.aspx

It is a good article because it helps with management and gets aquarist away from nutrocentric thinking and more holistic plant growth models.
It is understandable why folks/hobbyist make this/these assumption/s, but it's not helpful really to their goal.

If they have added nutrient dependency, it would become far far more difficult to test and make the conclusions.
We aquarist often have this issue.

So if we can rule out nutrients as limiting, and know the light PAR(using Tropica's suggestion , low to moderate light), we can get pretty good with dialing in CO2 with less troubles/dependent factors bugging us.
Sediment ferts also can help in this context.




Regards, 
Tom Barr


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## ReefkprZ (Aug 21, 2010)

I should have phrased my question better, I should have said "so your saying plants utilize nutrients even when they arent photosynthesizing" but thanks for that answer, it was right on the ball to organize my thinking. Plant photosynthesis and nutirents are much newer to me than symbiotic algae or say phosphates vs coraline algae.


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