Lucas Formula add back calculator here

had to make this for a friend so I figured I would post it here in case it can be of any help to any of the members.

This excel worksheet will calculate exactly the amount of nutrients needed to bring your resevoir to a target ppm, including adding water. This calculator assumes RO water...

For example, if you have a DWC bucket which you fill with 3.5 gals at 1400ppm, and you come back and there are only 2 gallons left and the ppms are reading 1000, this calculator will tell you exactly how much micro and bloom to add to your top off water (1.5 gallons in this case) to get the res back to your target TDS. It will also calculate lowering TDS. Say your res is down to 2 gallons and the ppms rose to 1600, now you want to bring them back down to 1300, this will accomplish that.

One thing to note, if you are trying to reduce the strength of your nutrient solution and the calculator gives negative values for the amount of micro and bloom, that means that you have to dump some of the res in order to get back down to that low ppm.

http://docs.google.com/fileview?id=...2ItNDZjZi00NTQzLTk4YjktN2ZmMmVlZTJjMjFl&hl=enhttp://rapidshare.com/files/351626704/ADDBACK_CALC.xlsx.html

Update: Calculator will now account for tap water. just enter your tap water ppm and it will adjust the mix for you.

Let me know if this is helpful
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I'd recommend putting it up on google docs and making it open for viewing.

Hey... this is what i have been needing!! I have been useing floranova, (GREAT STUFF) but want to use up my flora i have laying around in my ebb n flood... btw... Just what is the ppm's for lucas formula useing r/o and flora series?? THANKS!!!

tejashidrow said:

Hey... this is what i have been needing!! I have been useing floranova, (GREAT STUFF) but want to use up my flora i have laying around in my ebb n flood... btw... Just what is the ppm's for lucas formula useing r/o and flora series?? THANKS!!!

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Normally lucas says 0-8-16 for veg and bloom under HID lighting. That works out to 1326ppm @.7 conversion. This calculator will let you run any ppm and will tell you how much to mix. Many plants won't take 1300 during all phases of growth. I usually start off with 600 for about a week, and then start raising it.

What a great tool. Spreadsheets are a hobby of mine too! I've been thinking about making one since I saw the original addback formula lucas posted. I don't use Lucas formula so I never got around to it.

Great Job

I don't see the need or benefit of this since plants use each of the 16 elements in different proportions throughout their lifecycle. You wouldn't make a BALANCED nutrient solution by adding back.... Assuming after 4 days your plants had used 25% of the Volume of the Nutrient Solution is the system, you would maybe add 25% balanced to 75% totally out of whack.

So, all the Nitrogen is gone, and the plant hasn't used much Potasium, hypothetically. You do the add back. Now you have 175% of the required Potasium, and still only 25% of the required Nitrogen?

Or am I missing something?

Bud Spleefman said:

I don't see the need or benefit of this since plants use each of the 16 elements in different proportions throughout their lifecycle. You wouldn't make a BALANCED nutrient solution by adding back.... Assuming after 4 days your plants had used 25% of the Volume of the Nutrient Solution is the system, you would maybe add 25% balanced to 75% totally out of whack.

So, all the Nitrogen is gone, and the plant hasn't used much Potasium, hypothetically. You do the add back. Now you have 175% of the required Potasium, and still only 25% of the required Nitrogen?

Or am I missing something?

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I never change my res throughout the grow, or sometimes just once at the end of veg. Lucas also says he doesn't change the res with the add back method. Alot of people who add back nutrients instead of water don't change res solution. I never have any problems...

bendoslendo said:

What a great tool. Spreadsheets are a hobby of mine too! I've been thinking about making one since I saw the original addback formula lucas posted. I don't use Lucas formula so I never got around to it.

Great Job

Click to expand...

Lucas' formula for add back was based on discount/markup math and was somewhat inaccurate since it didn't take water volume into account. The formula i used is different and doesn't over or under shoot the nutrient levels, but requires the volumes of fluid to be input.

Bud Spleefman said:

I don't see the need or benefit of this since plants use each of the 16 elements in different proportions throughout their lifecycle. You wouldn't make a BALANCED nutrient solution by adding back.... Assuming after 4 days your plants had used 25% of the Volume of the Nutrient Solution is the system, you would maybe add 25% balanced to 75% totally out of whack.

So, all the Nitrogen is gone, and the plant hasn't used much Potasium, hypothetically. You do the add back. Now you have 175% of the required Potasium, and still only 25% of the required Nitrogen?

Or am I missing something?

Click to expand...

Then how would anybody ever grow in an auto top off ebb and flow system? Or any other system that doesn't drain to waste? That is the purpose of having the proper nutrient profile...I understand what you are saying, but in practice it works fine so long as you are using a balanced set of nutrients, like the lucas formula or GH 3 part or whatever. Also this would be used to top off a resevoir in a larger system as.

superusa said:

I never change my res throughout the grow, or sometimes just once at the end of veg. Lucas also says he doesn't change the res with the add back method. Alot of people who add back nutrients instead of water don't change res solution. I never have any problems...

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I'm not sure what Lucas himself does, but I did first learn about DWC and hear of the the Lucas Formula/Ratio and also the Highgrade/TrainOne/RubberChicken ratio on Overgrow.com. Every plant is different, some use more of one nutrient than another, and some use very little nutrients at all. My experience has been that, in general, with the well over 50 strains I have grown, that you are much more likely to overfertilize than under fertilize. So, safer to let them go a little hungry and top off with plain water than feed them EXTRA ferts every 4 days, and then every 7 - 10 days just do a complete change-over. Have you tried topping off with plain water? Even with topping off with plain water, I still get INDICAS that show signs of overfert almost every time I grow them. I can't imagine what they'd do with extra elementally rich solution.

Just my 2 cents, with all due respect. Whatever works for you and your strain(s) is what you should do.

superusa said:

Then how would anybody ever grow in an auto top off ebb and flow system? Or any other system that doesn't drain to waste? That is the purpose of having the proper nutrient profile...I understand what you are saying, but in practice it works fine so long as you are using a balanced set of nutrients, like the lucas formula or GH 3 part or whatever. Also this would be used to top off a resevoir in a larger system as.

Click to expand...

I would do this with plain, PH adjusted water. My profile has some pics at 7 days, all those plants are at 21 days now, so I'll post some pics when the lights come on tommorow, they are huge. And I am very light on the nutes, like 1150 ppm, topping off with plain water. It works well, and the buds taste great. You do know not all nutes are translocateable, ie: some shit can't be flushed??????!!!!!!! If you overfeed your buds will taste like crap.

Bud Spleefman said:

I'm not sure what Lucas himself does, but I did first learn about DWC and hear of the the Lucas Formula/Ratio and also the Highgrade/TrainOne/RubberChicken ratio on Overgrow.com. Every plant is different, some use more of one nutrient than another, and some use very little nutrients at all. My experience has been that, in general, with the well over 50 strains I have grown, that you are much more likely to overfertilize than under fertilize. So, safer to let them go a little hungry and top off with plain water than feed them EXTRA ferts every 4 days, and then every 7 - 10 days just do a complete change-over. Have you tried topping off with plain water? Even with topping off with plain water, I still get INDICAS that show signs of overfert almost every time I grow them. I can't imagine what they'd do with extra elementally rich solution.

Just my 2 cents, with all due respect. Whatever works for you and your strain(s) is what you should do.

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I am not knocking the water top off method. Lots of people use it with great success obviously. I personally use a 100% top off method.

In reference to overfeeding and such...

I don't automatically use the 0-8-16 that lucas reccomends. I just use the micro and bloom at a 1:2 ratio to achieve my desired ppms. I generally start plants in a 600 ppm solution, and then raise it based on the actions of the plant. If I fill the bucket with 600ppm solution, come back and it drinks a gallon and the ppms are below 600 now, then that means that the plant is drinking nutrients faster than it is drinking water, which means that i need to increase the strength of the nutrient solution. I continue doing this until the readings stay the same even when the solution level drops. i.e. i put 3.5 gallons in a bucket @ 1000ppms, i come back and only 2.5 gallons remain but the ppms are still 1000. That means the solution is balanced to the plants rate of uptake. This also eliminates pH swing since the conventration of the nutrients remains the same.

Now if I had 1200ppms in the bucket and came back and a gallon was gone and the ppms had risen to 1400, that would mean that the plants was drinking the water faster than the nutrients (which means you are overfeeding), and I would then lower the solution to 1100 or so to find the balance.

In this method you NEVER experience overfeeding, because the plants are only getting the level of nutrients they want, and you can see the movements of the concentration before any effects would normally be visible on the leaves of the plant.

Bud Spleefman said:

My experience has been that, in general, with the well over 50 strains I have grown, that you are much more likely to overfertilize than under fertilize.

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I do agree with this. That is why I use the TDS meter to track whether the solution is increasing or decreasing in strength. and I would never start a plant in the 0-8-16 solution that lucas reccomends, that solution is 1325ppm @.7 and is much too strong for any plant I have encountered, at least until the plant has vegged a couple weeks minimum.

superusa said:

Lucas' formula for add back was based on discount/markup math and was somewhat inaccurate since it didn't take water volume into account. The formula i used is different and doesn't over or under shoot the nutrient levels, but requires the volumes of fluid to be input.

Click to expand...

Oh look at you and yer fancified new-fangled formula!

((target ppm - current ppm) / target ppm) * micro ml (per gal) * res gals. = micro add back
((target ppm - current ppm) / target ppm) * bloom ml (per gal.) * res gals. = bloom add back

res gals in us format, ppm's at .7 conversion (i think)

I use rez recipe instead of lucas but the same goes...i suppose for me micro is 6, bloom is 9 (ml) and res gals is usually 10.57 depending...

my ec is good at 1.4 (cant rmr the ppm,i usually look at a chart someone posted around here) and when it drops suppose with top offs or feeding, the addback calculated above is almost always bang on...(near r/o would be helpful but i also cater to my waters starting ec of 0.4 before using the ppms in the target - current

bendoslendo said:

Oh look at you and yer fancified new-fangled formula!

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It's definitely not a fancy formula. Just a basic formula that uses volume of water. Without using the water the other formulas will overshoot or undershoot the nutes.

0-8-16 in 1 gallon of 0ppm water comes out to 1326@.7
divide the 1326 by 8 (amount of micro) and you get 165.75

This means that if you take 1 gallon of water and add 1ml of micro and 2 ml of bloom you will get 165ppm. The math from there is straight forward...

divide the target ppm by 165.75 and you get the number of ml of micro needed to make 1 gallon at the target ppm (multiply micro by 2 to get the bloom) Multiply that by the number of gallons you need to make. This figures the water that you are adding.

The calculator also adjusts for what's already in your res, using the same method. if you have a gallon left in your res and it is at 800 ppms and your target is 1200, it finds the difference, (400) divides by 165.75 (2.4ml of micro, 4.8ml of bloom) and adds that back to the amount of nutrients you need and then multiplies that number by the number of gallons remaining in the res. If your res is higher than your target the opposite happens. If you res is at 1600 and your target is 1200, the difference is 400 again, except this time it is negative, and the
calculator subtracts the 2.4ml and 4.8ml from the total) It is dead on accurate, but requires you to have water levels marked on your res.

I didn't post this here to start a flame war or anything, I just thought it would be useful for new growers, or for people who prefer to top off with nutrients without having to keep checking the strength of the solution over and over till they get to their target ppm.

With this method, i take a sample out of my drain valve, check the ppms and ph, mix what the calculator says into another bucket, and pump into my res. takes about 4-5 minutes total, and i never have to lift a lid or check the ppms after i top it off. Like I said I just thought it would be helpful to others. I had been doing the math in my head, but i had to make this calculator for a friend who sucks at math and has 10 plants in buckets at his house. He was sick of having to do the guess and check method when topping of his res, so i made him the calculator. Figured I would post here in case it helped anybody else.

By all means anybody who is growing successfully should stick with what works for them. If anybody here does use the nutrient top off method, feel free to give this a wing, it could save you some time.

Maybe you didn't see the

Maybe jokes should go in italics

When I try Lucas again, I will use your calc. Thx

bendoslendo said:

Maybe you didn't see the

Maybe jokes should go in italics

When I try Lucas again, I will use your calc. Thx

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It's all good. I figured you were kidding, but the other guy seemed to get upset at the idea of the nutrient top off method. Like I said the formula is not anything fancy lol, but it does work, and will put you dead on your ppms if you know your water level and current ppms. If you end up using it let me know how it works for you. I have been using this formula for a while now as well as a buddy of mine, and we have checked it against actual results several times. If needed I could change it to account for tap water too if that would be helpful to anybody....

Updated to account for tap water. Just enter your starting ppms and it will adjust for you.