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Chucks calculator vs Nutri-calc

N

newfyman

Seedling
Joined
3 Mar 2008
Messages
12
Location
Chesterfield
Hi
I had just started dosing EI and nothing seemed to be happening so after looking through lots of posts and articles again I realised that the calculators give different results.So for my 600ltr tank using Chucks calculator here's what I was adding 3x per week:
suggested target level 5ppm nitrate 1ppm phosphate
0.20 teaspoon of KHP204
1.00 teaspoon of KN03 ( the calc says 0.80)
Then adding 1 teaspoon traces from AE every other day as per AE's instructions.
From the Nutri-calc I am now adding 3x per week:
suggested target level 20ppm nitrate 3ppm phosphate
0.5 teaspoon of KHP204
1.5 teaspoon of KN03 ( the calc says 1 1/1?)
Traces as before
These are all being added straight to the tank as the tank is quite big I thought it would give me some room for error of the teaspoons not being exact. I know theres not that much difference between the amounts but things do seem to be getting better some pearling now.Do these amounts seem ok? Think I just need to re-assured really I thought all calcs would be the same and should always aim for 20ppm nitrate and 3ppm phosphate but the chucks one aims lower and you can't change the levels.
Thanks
 
Hi newfyman,
Welcome to the forum! 😀
There are major differences because chuck assumes different lighting that the lighting assumption used to develop EI. EI assumes max lighting, like around 5 wpg T5 on a 20 USG tank. I don't think Chuck used these lighting values. Also, because of his lower light assumptions Chucks nutrient levels don't have to be as high. The EI target ppm under max lighting is 20 ppm weekly NO3 for example.

If you have higher lighting over your 600L than about 150 watts T5 (more or less) you'll have better luck if you use the NutriCalc and you can save money by deleting the K2SO4.

Another factor is that large tanks really suffer the problem of poor flow and circulation. Under low lighting this is not much of an issue but as the lighting increases these tanks suffer greatly. Therefore, as incredible as it seems, you actually have less room for error in a big tank because of inefficient nutrient and CO2 delivery to the leaf surface. Your only margin of error is if you have massive pumping power. The more flow, the less stagnant areas that there are.

I'm an extreme example but just as reference, my 600L, situated in a conservatory is powered by 1/2 kilowatt of T5 CF bulbs fitted with gull wing reflectors. I have a total filter flow "rating" of nearly 4000 LPH. If I were to use only the Nutricalc values it would be insufficient. I use nearly quadruple the NO3 value, just under triple the PO4 value and just over double the trace value that Nutricalc suggests. This is a clear indication that my flow is still inefficient for this level of lighting and biomass. My CO2 is injected from both sides at high rates.

Now, I'm not saying that you need to follow my crazy example because you may not have as much light and the type of plants you are trying to grow may be less sensitive but it's just to illustrate that there are a lot of variables and in a big tank you will have to refine your numbers until you get it right. Getting the dosing right is easy though compared to getting the CO2 right. Your problem may actually be there instead. None of these dosing calculations are cast in concrete. They are simply very useful guides. Some can get away with less and others need more. 😱

Cheers,
 
Thanks Clive for the in depth answer you gave me and for the replies you have given to everyone else, they have formed most of my reading over the last few weeks.
Sorry, I should have provided more info on the tank which is 50x24x30" high, this will add to the distribution problem and lighting.It also has glass covers which again will drop the lighting but hopefully is helping with the C02 (see my other post Drop checker green).
The filters are 2 x Ehiem proffesional 2 950 litres per hour, so if you half it, 950 litres on a 600ltr tank, I am way off the 10x turnover rule but 90% of the plants are moving.
The lighting is 3 x 54w T5 (2x power glo, 1x life glo) with reflectors. Medium to heavy plant load, lots of weeds until I get it on the right track.
Back to the dosing, as you say the amounts can be very variable but where do I start?
Then I need to wait three weeks, then I can back off with the dosing, look for deficiencies, then add slightly more but, if in the first place I were adding way to much, how would I know? Test for nitrate 😉 ?
I am confused on this!!
Also, I'm adding the powder dry, with level teaspoons direct to the tank, is this accurate enough?
Thanks
Barrie
 
Hi Barrie,
Don't get confused 😀 I vote for starting with the Nutricalc numbers. Your lighting is medium so the nutrient uptake demand is not nearly as extreme as it is in my tank, but might be higher than Chuck's assumptions.

Adding level teaspoons is accurate enough. So for the next three weeks look closely at the tank. Look closely at the substrate in front:

Are you are seeing small patches of BGA starting? If so, 50% (or more) water change, clean and immediately double the nitrate.

Are you starting to see GSA on some of the leaves? 50% (or more) water change, cut them off and immediately double the PO4.

Are you starting to see hair/thread or disintegrating stems/leaves? 50% (or more) water change and up the CO2 bubble rate.

As you make these dosing adjustments re-start the clock so that the three week assessment period rolls on. The quicker you catch the algae germination the better of you will be and the shorter the adjustment time. If you don't pay attention and an infestation rolls in it will take longer to eradicate.

There is not a problem if you have too much nutrients because nutrients don't cause algae remember? Now, say you doubled the NO3 and you really didn't need that much: the only ramification is that you are wasting NO3.

After a few months you should have a clear tank and you may only have algae on the hardscape and maybe a little bit on the front glass. This is about as good as it can get, but you may want to back off the nutrients. How to accomplish that? Well, definitely forget about test kits, that's for sure :shock: Start backing off by some easy fraction of a teaspoon - say 1/2 teaspoon. So if 2 teaspoons of NO3 got you to an algae free condition then try 1.5 teaspoon for three weeks and see if BGA comes back. If it does then you know that 1.5 teaspoons doesn't work and go back up to 2.

If three weeks at 1.5 teaspoon didn't cause BGA then back off another 1/2 teaspoon and see how that works for 3 weeks. You can do the same exercise with PO4 and traces.

But there are complications. Increased CO2 causes a demand for more NO3/PO4. Decreased PO4 dosing causes a decreased demand for NO3 and vice versa. This is known as "coupling". Nutrients are coupled because they are all feeding the same machine.

Another complication is that as the plants grow you have higher biomass. High Biomass is both boon and bane. Boon because it supports higher bacteria population and directly removes more ammonia. Bane because more biomass must be fed more. Your margin for dosing error is actually less as your biomass increases because there are more leaves to be fed. You will find therefore that you won't be able to back off the nutrients as much as you thought you might have 3 weeks ago because there are more mouths to be fed. :idea:

You are more likely to discover that you need to add more nutrients and CO2 as time goes on. That's one reason I never bother with trying to back off, even when I prune the tank. I reckon that if I'm adding 30% more nutrients than I need, who cares? That means 30% less chance of having to scrub algae off my plants due to deficiency. Dry powders are cheap(ish) so the penalty is really not that bad.

Hope this makes sense. 😀

Cheers,
 
Some day I'll path analysis for all the major parameters(light, CO2 and nutrients) and how % they influence the plant growth model.

Some day.........

Regards,
Tom Barr
 
Looking forward to it Tom! First things first though. "Analysis of Sediments Part II" - Way overdue 😀

Cheers,
 
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