So...

I am a first time farmer but am using a pretty sophisticated aeroponic/nft system. I am 9 weeks into it and will begin my third week of flowering tomorrow. I had major nute burn issues during the last couple weeks of vegetation at only 400ppm using GH Maxi Gro with an organic inoculant.

So does anyone know the max ppm an aeroponic system should provide?

What is your grow medium? Rockwool will hold onto the nutes, building up salts which will burn the roots. I cut my starter cubes in half, and use 4" nets with hydroton. But since then, I found www.suretogrow.com. I have not seen any testimonials, but their products seem ideal

As the below shows GH grow formula is a very deficient nutrient formula for aeroponic or soil-less hydroponic. It contains no micronutrients I or calcium. I imagine you are having pH problems with the use of just their grow formula as it contains no calcium to form pH buffers so low pH is likely an issue.

As cam be seen, no combination of GH formulas will produce a mix containing al nutrients need/recommended but a mix og Bllom and the Micro comes close.

Product Name MICRO BLOOM GROW HWMICRO
Grams/ml liquid 1.22691 1.14894 1.1124 1.15076

NO3 Nitrate 4.7% 00% 1.75% 3.7%
NH4 Ammoniacal 0.3% 00% 0.25% 0.3%
NH2 Urea 00% 00% 00% 1.0%
Total N 5% 00% 2% 5%
P (as P2O5) 00% 5% 1% 00%
K (as K2O) 1% 4% 6% 1%
Mg 00% 1.5% 0.5% 00%
S 1% 00% 00% 00%
Ca 5% 00% 00% 1%
Fe 0.1% 00% 00% 0.1%
B 00% 00% 00% 00%
Mn 0.05% 00% 00% 0.05%
Zn 00% 00% 00% 00%
Mo 0.0008% 00% 00% 0.0008%
Na 00% 00% 00% 00%
Cu 00% 00% 00% 00%
Cl 00% 00% 00% 00%
Co 0.0005% 00% 00% 0.0005%

B=absent from MICRO & HWMICRO guar analysis but potassium borate listed as a derivative.
Zn=absent from MICRO & HWMICRO guar analysis but zinc nitrate listed as a derivative.
Cu=absent from MICRO & HWMICRO guar analysis but copper nitrate listed as a derivative.

Many people have success using a mixture of Bloom and Micro nutrients from GH.


General Hydroponics Flora Series Feeding Strategy - Lucas Formula
by: Lucas

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)

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.

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.

IMHO it is better to just maintain water levels daily and maintain adjusted pH. I typically change nutrients once or twice a week and do disinfection rinses each time rather than adding nutrients to old nutrient solutions. I have and stll do run rooms using both methods but have less problems and higher yields with the systems with frquently changed nutrients.

Thank you so much for the tutorial. I do change my res every week and adjust ph levels twice a day; once in the morning and once in the afternoon. So far so good. They are at 3feet and its only been 9 weeks! I am a proud father and will go with the info. Thanks akfatman.

PS. What does TDS @ .5 conversion mean? I know what TDS indicates but do not know what the @ .5 conversion means?

@.5 means at an electro conductivity reading of 0.5 the TDS (ppm will read at such and such a number. Most Conductivity meters can give readings in Ec/TDS/ppm/ or mg/L.

TDS or Total Dissolved Solids is a measure of the total ions in solution. EC is actually a measure of the ionic activity of a solution in term of its capacity to transmit current. {b]In dilute solution,[/b] TDS and EC are reasonably comparable. The TDS of a water sample based on the measured EC value can be calculated using the following equation:

TDS (mg/l) = 0.5 x EC (dS/m or mmho/cm) or = 0.5 * 1000 x EC (mS/cm)

As the above equation does not necessaryily apply at higher concentrations you will often see the expression @.5 or @.7 referring to what the ppm will be at those EC readings as the ratio changes with stronger concentraions of ionic salts.

Got it! Thanks for clearing that up. I will post some pics to let you know the progress.Can we post pics on this website and is it safe?

Just always remember; deny, deny, deny. And of course fo not include your face in self-incriminating photos.

Yo akfatman, is there any other way I can communicate with you out of this forum? An email or facebook account? I would like to keep in touch with you throughout my work. I have some new things under my sleave. Hope to share. Let me know so I can send pics.

Salute

when topping off like you said do you add the 56ml micro to bring up the ppm.so if i was tooping of i would do 64ml.if add new nutes to 1 gal H20 56 for the refresh & 8ml for the new gal of h2o.so for bloom it wold be 106 refresh & 10 for new.trying to make sure have it right.if not please tell me.thank you all

The topping off is based upon your never changing your nutrient water but instead just topping the resrvoir off with fresh water daily and After your ppm has dropped to a level you choose as too low you then you each time must aclculate how much to add based upon your initail and present ppm readings add additional nutrient concentration to the nutrient resarvoir. Yes it is always added at a two parts micro to one part bloom by Lucas formula method. This means you only empty the reservoir out between grows.

However unless you are using a very small nutrient reservoir for a large number of plants there is no need to add nutrients if you instead just change the nutrient water when the ppm level drops too low.

I just consider the above nutrient addition method (Lucas Formula Method) as the cheap skates method or the too stubborn to mix your own nutrient formula method. I only use the method for remote grows where the nutrient, ph and water levels are all controlled by industrial controllers that contri ol the feed pumps. They out put read out signals as well as alarms to a lap top computer. The lap tops sends alarms to email addresses for alerts. I do not use the AN or GH formulas and I mix my formulas up so that I use a equal amount of each of a two part formula to my nutrient reservoirs. I also do not mix up a sepearte formula for Vegetaive growth versus Bloom but I do add a buffer to my blloming reservoir nutrients that I do not use with the grow nutrients. Otherwise I use the same nutrient formula throughout thr grow but at different ppm's. My initail nalysis is not the same as GH or AN so ml ammounts I add are different from above. AN and GH I believe have formulas mixed at 1:100 whereas I mix at ratios of 1:250 ie I make my concentrates two and one half times stronger so I add 1/4 as much for the same results.