NO3 (or other) uptake rates vs light levels??

[Laith]

A question here re uptake rates vs light levels.

For example, I see a pretty consistent EI recommendation of 1/4tsp of KNO3 3x a week per 20g (or more usally 1/2 tsp 3x a week for a 55g). That's 10mg/l of NO3 per dose or 30mg/l per week.

And 10ml of CSM+B 3x a week (at a concentration of 1tbsp in 250ml) gives you around 0.2 mg/l of Fe per dose or 0.6mg/l per week.

This recommendation is based on uptake at what light levels? I find it a bit difficult to accept that one should use the same dosing at 2wpg as at 6wpg...

I would think it would be useful to have a recommendation for different wpg levels. I know that there are other variables that influence it and that wpg is not that great an indicator of lighting, but it would make sense to have a dosing recommendation based on lighting levels, no?

I have a heavily planted 200l tank (about 175l net volume) with 5x 25w NO flourescent tubes (T8s) on it. That gives me about 2.3wpg. Should I still dose the same amount of KNO3 as recommended above? Given CO2 at >30mg/l and sufficient levels of other nutrients, does 2.3wpg induce such an uptake rate?

 

[chubasco]

Re: NO3 (or other) uptake rates vs light levels??

Laith,
If I'm not mistaken that's for high light tanks (5wpg and up). EI can still be
used for lower light tanks, just lower the frequency of dosing: you would
dose once instead of 3 times per week, and increasing frequency, if needed.

Bill

 

[Laith]

Re: NO3 (or other) uptake rates vs light levels??

No, don't think so. I've seen it recommended for tanks with just over 2wpg as well as tanks with ranges from 2.2 through to 3.2 (and higher of course).

And the recommended dosage does not change much across the range of lighting, therefore my question...

And as to altering the dosage, I had thought that you should keep the frequency but vary the amounts. Now I'm not sure about things anymore...

 

[chubasco]

Re: NO3 (or other) uptake rates vs light levels??

Sorry, Laith, I think I've confused CO2 and nonCO2 tank ferting With
50% weekly WC, does it matter? Since you're resetting the values weekly(?)
I'm wondering if it simply means your tank's plants won't grow as fast, but
still be healthy growth compared to high-light tanks.

I would like clarification on high/lo tank lighting. I've always gone with:
1-2wpg=low
3-4wpg=medium
5&up=high
Those with 5&up/wpg seem to push the envelope on CO2 enrichment.

Bill

 

[Laith]

Re: NO3 (or other) uptake rates vs light levels??

I think it does matter, even with the 50% water changes. If you're dosing 30mg/l NO3 per week, the theoretical maximum NO3 that can be reached with 50% weekly water changes and *no* uptake is around 60mg/l...

If you have an uptake of 1mg/l per day, the theoretical maximum is still up around 45 mg/l. An uptake of 2mg/l gives you a maximum of around 32mg/l. 3mg/l per day gives you around 18mg/l. 4mg/l per day is 12mg/l, etc.

So are we saying that if you don't have an uptake of 3-4mg/l per day then there is a problem?

 

[chubasco]

Re: NO3 (or other) uptake rates vs light levels??

So are we saying that if you don't have an uptake of 3-4mg/l per day then there is a problem?

And we haven't even addressed the bio-load in the tank as to fish, shrimp,
snails, etc, what amount of nitrates are being added by feeding and excreting

 

[Laith]

Re: NO3 (or other) uptake rates vs light levels??

Exactly...

So, Tom, you want to give us your input on this?

 

[Urkevitz]

Re: NO3 (or other) uptake rates vs light levels??

Good question, I tend to underdose fearing I might have an accumulation by the end of the week. I have heard that cherry shrimp cannot survive nitrate levels above 20 ppm.

 

[Vladimir Zhurov]

Re: NO3 (or other) uptake rates vs light levels??

In EI article Tom's example is "a typical routine for a high light tank with low fish load", 5.5 wpg, 20 g tank.

I think there is no single scheme that one can make and then get "correct" doses from inputing "tank dimensions" or "amount of light" into it just because there are too many factors that one has to consider. Even in the example above - what is plant biomass, what is exactly "low fish load", what kind of plants was used, and so on.

The only thing which can be considered constant are target and desired levels of NPK, CO2 and traces listed in the article:

CO2 range 20-30ppm
NO3 range 5-20ppm
K+ range 10-30ppm
PO4 range 0.4-1.5 ppm
Fe 0.5ppm or higher (?)

I personally believe that at initial stage you have to do some testing of nitrate and phosphate levels to estimate uptake rates of your particular tank, get idea of your tap water parameters. And then just decide what will be your desired range of nutrients and start dosing at amount and frequency required to get to this range. If you will have to scale things relatively to the EI article recommendations apply the same factor to all elements and do not bother with testing of potassium or iron levels. I personally use nitrate level as a "guide" and scale things in parallel.

And note that recommended ranges are quite wide as plants are very flexible and have great adaptability.

Regards.

Vladimir.

 

[Tom Barr]

Re: NO3 (or other) uptake rates vs light levels??

A question here re uptake rates vs light levels.

This recommendation is based on uptake at what light levels? I find it a bit difficult to accept that one should use the same dosing at 2wpg as at 6wpg...

Why? You maybe wasting a little, but we are doing that to some degree no matter what. Excess does not cause problems, otherwise we'd all have problems with any method.

If you have 2w/gal, you can add less and dial things down slowly till you get a negative effect.

More experienced folks can do this and after seeing what good rich conditions provide in terms of plant health, they know what to look for.

I would think it would be useful to have a recommendation for different wpg levels. I know that there are other variables that influence it and that wpg is not that great an indicator of lighting, but it would make sense to have a dosing recommendation based on lighting levels, no?

If you want, nothing wrong with that, I've seen some good uptake rates with low light also though.

I have a heavily planted 200l tank (about 175l net volume) with 5x 25w NO flourescent tubes (T8s) on it. That gives me about 2.3wpg. Should I still dose the same amount of KNO3 as recommended above? Given CO2 at >30mg/l and sufficient levels of other nutrients, does 2.3wpg induce such an uptake rate?

It'll go pretty good and yes, just try this amount for now and then slowly back off and see.

Make changes over at least 3 week time peroids.
Note plant health carefully.

Regards,
Tom Barr

 

[ervis]

Re: NO3 (or other) uptake rates vs light levels??

More experienced folks can do this and after seeing what good rich conditions provide in terms of plant health, they know what to look for.

It'll go pretty good and yes, just try this amount for now and then slowly back off and see.

Make changes over at least 3 week time peroids.
Note plant health carefully.

Regards,
Tom Barr

Okay, I'll be a guniea pig. I've been growing wet weeds for only 4 months now and while I've learned alot, I cannot make these observations with any degree of accuracy. For me, they're either growing profusely, not growing, or dying.

I slackend off for a while on my dosing and after a couple of weeks I noticed that I'd removed all of the Ludwigea Repens. All of it had been slowly dying and the Bacopa and Rotalla were also becoming stunted. The Hygro P. was growing with abandon.

So I'm on a more regimented dosing schedule now and still battling the thread algae that also cropped up during this time. It's hard to say if I'm in the ball park or not. The hygro is still growing rapidly, the Bacopa and Rotalla are still stunted. What else am I looking for? It's hard to judge if the Rotalla is responding, I have to cut the tops off because they're full of thread algae.

steve

 

[Tom Barr]

Re: NO3 (or other) uptake rates vs light levels??

Often, the stunted tips don't come back, I trim off anything ugly or too infested with algae to be worth the trouble.

As you said, things will grow propfusely, it sometimes takes a week or two to get things going, but when they do, you are back on easy street.

If you keep up on things, you seldom have issues.
Later,. after you get more of a feel for the plants and their growth rates(each species is unique in it's growth habits), you can reduce the levels of ferts to meet the demands.

For now or if you have algae and other issues, do big changes to the tank or want to whip it uop for an open house or a photo shoot etc, then weekly or 2x a week water changes with dosing every other day will amp the tank into overdrive.

We all negelect tanks at some point, but the old timer knows what they have to do and it's the same old hat over and over again.

How far you can go without having to do so much work is often a goal of many.

Regards,
Tom Barr