ebb and flow reservoir size

ForcedInduction

Active Member
i am following the lucas formula exactly, here it is from the man himself-

General Hydroponics Flora Series Feeding Strategy - Lucas Formula

G-M-B (Grow-Micro-Bloom)
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)

Example:

((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.
 

GypsyBush

Well-Known Member
i am following the lucas formula exactly,
Than you shoud follow what Lucas says... EXACTLY...:lol::clap:

first flood with the lucas formula! as you can see i also raised my flood depth a bit.

i did this trying to coax the roots up higher in the pots.

they don't seem to be bothered by the extra depth, i have already done about 5 or 6 floods at this depth
Should be fine as long as you do not have RW or any other highly absorbent medium to get soaked...:razz:

If you ever use RW or similar, you should stop the flood 1/2" below the medium...

like this...:razz:


 

ForcedInduction

Active Member
Than you shoud follow what Lucas says... EXACTLY...:lol::clap:



Should be fine as long as you do not have RW or any other highly absorbent medium to get soaked...:razz:

If you ever use RW or similar, you should stop the flood 1/2" below the medium...

like this...:razz:



thats what i'm trying to do! :mrgreen:

which add back method would you use?


adding full strength nutrient solution back and changing the res every grow cycle,

or adding just PH'ed water and changing the res when you have added back an amount of water equal to your res size.
 

GypsyBush

Well-Known Member
which add back method would you use?


adding full strength nutrient solution back and changing the res every grow cycle,

or adding just PH'ed water and changing the res when you have added back an amount of water equal to your res size.

I do no thing...:razz:

I have a HUGE res... that stays stable and plenty full for well over 2 weeks...

I do not top off... ever..:lol::clap:

nope no rockwool or anything, just hydroton and roots
Perfect...:clap::clap:
 

GypsyBush

Well-Known Member
I don't even know who Lucas is..:shock:... much less what he recommends...

But as I said.. I recommend topping off with straight water (ph'd of course)...

AT MAX.. 1/4 strength...

But I already told you this and you didn;t like it...:roll:... ... :lol::clap::razz:
 

ForcedInduction

Active Member
I am using 0-8-16 GH Lucas in flower and find that my nutrient PPMs are climbing every day as the water evaporates. I have been just adding full strength nutes. How best to reduce this ppm upward creep?
> Just weaken the nute PPM that I top off with?

yes, to one third of original 0-8-16.. try 0-2-4 in your addback water
This is a strategy that DOES require a TDS meter.

you are using a strategy that seeks to maintain the TDS between 1100 and 1400 ppm on a .7 conversion meter, for the life of the crop. If your TDS goes over 1800, you should water down your nutes.. add only water with no nutes

> Just checking, but what is the maximum PPM my plants can tolerate?

things get ugly above 2100ppm @.7 conversion, which is EC 3000, and also equivalent to 1500ppm on a .5 conversion meter. YOU MUST account for the conversion factor of your meter.


more helpful quotes from the ask lucas thread
 

Dapps420

Member
Than you shoud follow what Lucas says... EXACTLY...:lol::clap:



Should be fine as long as you do not have RW or any other highly absorbent medium to get soaked...:razz:

If you ever use RW or similar, you should stop the flood 1/2" below the medium...

like this...:razz:

hmmm Interesting........ I think that may be a large problem of mine. I think I may be flooding too high up on my rockwool medium. Im flooding to at lest 1/4 to 1/2 way up the rockwool................... And it seems my guys are a bit over watered :-?... At least it seems that way, Check out my thread there are pics of my plants, and it seems like their leaves are pointing down. Also I have some sort of deficiancy in my solution that is causing the leaves to burn at the tips and turn yellow eventually (check out the pics please :)). THANKS for your help folks!
 

ForcedInduction

Active Member
here are some pics i just took. the stems are really swelling up!!! :mrgreen:

the biggest ones are all 24 days old today.
 

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