Lucas Formula

Discussion in 'Hydroponics / Aeroponics' started by sealfever42, Jan 11, 2007.


    sealfever42 Active Member

    General Hydroponics Flora Series Feeding Strategy - Lucas Formula

    G-M-B (Grow-Micro-Bloom)
    0-5-10 - For Vegetative cycle (18/6)
    0-8-16 - For Flowering cycle (12/12)

    The numbers above indicate the number of milliliters (ml) of Flora Grow, Micro or Bloom formulas that I use in one gallon (US Liquid) of nutrients.

    You will notice I dont use any of the Flora “Grow” formula, do not need to, the Flora "Micro" provides plenty of Nitrogen.

    There are two ways to work with this formula:

    1. Top off the reservoir daily using a pH corrected water solution as required to maintain full reservoir level. After adding back an amount of water equal to the amount of your reservoir capacity you should change the reservoir and put in fresh solution.

    2. Top off the reservoir daily using a pH corrected 100% strength nutrient solution as required to maintain full reservoir level. Continue to use this nutrient solution without dumping the tank unless the PPM rises above acceptable levels.

    Between vegetative and flowering cycles you should dump your nutrients, then flush (possibly with Clearex) to remove salt buildups, then change to the other feeding program. Always shake your GH nutrient bottles before using them!

    For young plants, just transplanted into the hydro setup, give them 50% strength nutrient mix to prevent overfeeding them while their young. Gradually bring up the mix to full strength as they grow over the next few weeks or so.

    The lucas formula is normally intended for use with RO or near 0 PPM water.

    NOTE: The Lucas formula eliminates the need for Epsom salts to correct (Magnesium) Mg deficiencies in most normal feeding programs recommended by manufacturers. Cannabis needs a lot of Magnesium to thrive.

    The Flora Micro is providing the Nitrogen and the Magnesium in the proper balance, thus there is no need for the Grow formula and little or no room under the maximum acceptable ppm limit of 1600 @ 0.7 conversion.

    Calculated EC/TDS levels:

    EC microsiemen:
    0-4-8: 946 µS
    0-5-10: 1184 µS
    0-8-16: 1894 µS

    TDS @ 0.5 conversion:
    0-4-8 = 473 ppm
    0-5-10 = 592 ppm
    0-8-16 = 947 ppm

    TDS @ 0.7 conversion:
    0-4-8 = 663 ppm
    0-5-10 = 829 ppm
    0-8-16 = 1326 ppm

    Addback Calculator - (For Advanced Users)

    Say you were running the 0-8-16 formula, at 0.7 conversion with a 22 gallon res. When you first fill it up, your ppm will be around 1330.

    Now you have been growing for a week, and some of the water has been taken up by the plants, some has evaporated, and now your res is at 947 ppm. You need to get your ppm from 947 to 1330. Here is the equation:

    ((target - current) / target) * 8 ml per gallon * res gallons = Flora Micro (ml) double this figure to get Flora Bloom (ml)


    ((1330 - 947) / 1330) * 8 * 22
    (383 / 1330) * 8 * 22
    0.3 * 8 * 22 = 53 ml Flora Micro

    53 ml Flora Micro, double that and you get 106 ml Flora Bloom. So 53 ml Flora Micro and 106 ml Flora Bloom to add back to your 22 gallon res to get you from 947 to 1330.

    Using Hard Water GH Micro

    I had been experimenting with using the Hard water Micro as a substitute for the normal Flora Micro, this to account for my hard 350 PPM water and the lack of a large enough RO filter at the time. It has worked well for me. I just kept my reservoir below 1150 PPM @ .5 conversion and its all good.

    One tip - do not pH down this stuff, the hard water micro will drop pH gradually over the next 24 hours, for example I mix up a batch, it is at like 6.2, the next day, its at 5.6-5.8 after running in the system for a while. If I pH downed that to 5.7 before putting it in the system, it ended up as low as 4.8-5.2 by the next day.

    My conclusion, the hard water micro was buffering the alkaline crud in my water, it just doesnot do it ASAP fast like the phosphoric acid. [​IMG][​IMG][​IMG][​IMG]
    [​IMG] [​IMG]

    Damion5050 Well-Known Member

    been looking for this formula tyvm..

    patjack Well-Known Member


    I think the first time I was reffered to the lucas thread was by earl on this site and wow, talk about eaaassssyyyy, after I read the (long) thread I went hydro and I will say I will never look back, using this system is so easy I will never change. No more soil for me (except outside):mrgreen:
    Blanca Deleon likes this.

    Damion5050 Well-Known Member

    What kind of hydro system you using, I am currently doing HB

    patjack Well-Known Member

    I am using bubble buckets=
    just a bucket with a bubbler and a 3in net pot in the top

    Damion5050 Well-Known Member

    What size bucket??

    patjack Well-Known Member

    five gallon buckets, one plant per so they can get bigger ( to stay under max plants for my area) I made them with all the drains and refills and crap but don't use those, from now on just buckets with a net pot and a small hole at the top for the airstone line to go through, I will say I have been following alot of the hempy threads and it sounds interesting, I will probably give it a shot in the future but for now this is working well for me.
    Cpip1218 likes this.

    Damion5050 Well-Known Member

    Yeah HB is a simple mans Hydro System, most of the time if you mix your chemicals right you dont ever need to check ph or anything just use R/O water and measure your nutes right and it does the rest..

    chunkdaddyo Active Member

    Can anyone tell me if I can change to the Lucas Formula in mid grow? I have been using Flora Nova Grow and now Bloom ( both by GH ).Things seem to growing well with the FloraNova except there is alot of undissolved matter in the bottom of reservoir. I hear that the GH FloraMicro/FloraGrow dissolves more fully. If I do change, should I use GH Florakleen for a day or two before changing? Any help would be appreciated.

    potroast Uses the Rollitup profile Staff Member

    Stick with the FloraNova, and stir a lot more. :blsmoke:

    HTH :mrgreen:
    rocko369 and Tim Fox like this.

    aeroman Well-Known Member

    any1 no if u can use the lucas forumula with ANs 3 part?

    hooked.on.ponics Well-Known Member

    Yeah, you can definitely use Advanced Nutrients' Grow, Micro, and Bloom plugged into the Lucas Formula. AN and GH use basically the same nutrient ratios.

    Personally, I'd be ready to supplement it with Magnesium Sulphate - you're not supposed to need extra Magnesium with the Lucas Formula, but it's better to be safe than sorry, imho. If you don't need it, nothing is harmed.

    aeroman Well-Known Member

    sweet ima try that next grow for shure

    always wanted to try lucas formula
    but i don like GH

    CustomHydro Well-Known Member

    It can be done with Pure Blend Pro also, actually it can be done woth any nutrient brand. U just need to use the conversion spreadsheet. I will look for it. I have it downloaded and all u do is type in the specs from the back of your nutes and it tells u how much to use to get u to this formula.

    This guy Lucas' has much more methods to his madness than listed here. Their are a lot of variables that are discussed in much mpore detail in this thread on cannabis world. I suggest anyone that tries this formula goes there to read up in more detail.

    IVkingXX Active Member

    ive seen a a few threads that with the lucas formula you dont have to check that correct?

    CustomHydro Well-Known Member

    Google "ask lucas" and u will find a nice thread by him...

    Yota Well-Known Member

    i don't understand how you would never need to change your rez

    CustomHydro Well-Known Member

    If your nute solution is kept at proper temps, and minimal organics are added u can go two full grows w/o changing out res (from what I hear). The third grow your plants start to look sick and pale colored I wouldn't go more than 8 weeks max IMHO, and if it starts to smell bad change immediately...
    If you decide to go this route you are putting your res out there as a bacteria magnet, changing the res, although not always neccessary is still the safest way to go.

    Matty10 Active Member

    Can I use the Lucas Formula if I have the Sensi Grow two part system and Sensi Bloom two part system? I am about to start my very first grow and someone recommended that I look up the Lucas Formula. If I can't use this formula is there another formula that I could follow?

    Can someone explain the 2 types of ways to use the formula? I am about to start my very first grow and it sounds like this formula might be the easiest for someone first starting out. Finally, what does the TDS conversion @ 0.5 and 0.7 mean and what should my PPM be at during the various stages if my water is at 270 PPM?

    Thank You


    mrduke Well-Known Member

    can i use this fumula with tap water around 300 ppm?
    when increasing the strenght from the starting clone to full veg do you just add more when topping off the res.?? little help with that would be great

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