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hydroponic cannabis with lucas formula

Hydroponics using Lucas Formula

Some don’t get it, others do… Regardless we are here to help you better understand the Lucas Formula.lucas method with GHE flora micro flora bloom

The Lucas Formula derives from a man named Lucas who participated in online forums for growers who use hydroponics/soil-less growing. His nutrient feeding regime quickly became widely recognised and spread like wild fire. People could see how well his methods were working with less effort being put into his grows yet still receiving the same great results. This formula uses only 2 parts of the General Hydroponics 3 part Flora series which is Micro, Gro and Bloom. 

Read: GHE (General Hydroponics Europe) re-branded "Terra Aquatica"

The Lucas Formula using General Hydroponics/EHG’s 3 part System

General Hydroponics/EHG make a 3 part series of nutrients consisting of Micro, Grow and Bloom. These 3 bottles you purchase would normally be used together through out the life cycle of your plant and receive great results if the instructions on the bottle are followed. However, Lucas figured out that you can leave the Gro out of the equation as there is enough nitrogen and all the other nutrients that the plant needs in the Micro that it can be used alone along with Bloom which also saves you from having to buy the Gro in the first place.

So, how does it work?

Your going to mix in 8ml’s of Micro (brown liquid) to 3.78 litres (1 gallon) of water and then mix in 16ml’s of Bloom (pink liquid) and your solution is ready to use. You’re growing in Coco? That changes things a bit. Scroll down a little further, we have covered how to adapt the method if your using Coco as your growing medium as well.

General Hydroponics have two dry nutrients called MaxiBloom and MaxiGro. Its been found that if you use MaxiBloom in the ratio of 7 grams per 3.78 litres (1 gallon) of water, it produces a very similar effect to the original Lucas Formula which we covered above. MaxiGro wouldn’t need to be purchased which makes it an easier and cheaper method to use.

Simply add 7 grams of MaxiBloom into a cup and dissolve it in some warm water and then add it to your 3.78 litres (1 gallon) of water. pH should then be adjusted accordingly once you have properly mixed in your MaxiBloom to ensure the most accurate readings.

Using the Lucas Formula and General Hydroponics FloraNova series

It is the easiest method to use but not as cheap as the Maxibloom. If your using General Hydroponics FloraNovaFloraNova Bloom 1 part system then mix in 8ml’s of FloraNova to your 3.78 litres (1 gallon) of water and your ready to feed.

The Lucas Formula with Coco Coir as your medium – Head’s Formula

Coco Coir naturally lacks calcium therefore a small amount of Cal-Mag mixed in to your 3.78 litres (1 gallon) of water will help to give the plants all the Calcium and Magnesium that they require before giving them their nutrients in order to get a good balance of exactly what your plant needs.

Alternatively, there is a modified formula that can be used specifically for Coco that uses a different ratio: Mixing 6ml’s of Micro and 9ml of Bloom per 3.78 litres (1 gallon) as well as 1 gram of Epsom Salts.

Both methods work well when using Coco but be sure to use the Head’s Formula if you start noticing any deficiencies whether they are pH or nutrient related.

Low light ratio & Flowering vs. Vegetative State

There is this misunderstanding that you should use 5ml’s of Micro and 10ml’s of Bloom when in vegetative state and then switching to 8ml’s of Micro and 16ml’s of Bloom when in flowering stage. The Lucas Formula ratio has been specifically designed to be used throughout your plants life cycle.

Lucas himself stated that the 0-5-10 ratio was for low light situations such as fluorescent lighting like PL/L (Phillips Lighting) and CFL’s (Compact Fluorescent Lighting), or HID (High Intensity Discharge) lamps less than 400W. The 0-8-16 ratio is meant for medium to high lighting 400W+.

Type of water used with the Lucas Formula

The original formula uses Reverse Osmosis (RO) water and is intended to be used without having to measure the pH and PPM (Parts Per Million). Reverse Osmosis water makes this possible because, in theory, it should be the same for everyone around the world. RO water is filtered water that has been forced through a semi-permeable membrane in order to remove a large majority of contaminates from the water. You can either buy an RO water filtering system or just buy bottled RO water. Alternatively, distilled water will also give great results which can be purchased at most convenience stores in your area. Only have tap water available? We have a look at how to adapt the formula below.

Adapting Lucas Formula for tap water

All you will need to do is make sure that the tap water is pH balanced as tap water differs in pH all around the world. Checking your pH with your meter and keeping it at around 5.8 should be the ideal pH for your plants.

Lucas Formula for your seedlings/cuttings

Cuttings or plants younger than 4 weeks old might not be able to handle a full strength feeding formula and you may need to dilute the nutrient solution before feeding them. However, make sure that you stick with the correct ratio’s when mixing your solution i.e 50% strength would be 4ml’s of Micro and 8ml’s of Bloom or 3.5g of dry MaxiBloom per 3.78 litres (1 gallon).

Using additives with the Lucas Formula

Additives can be incorporated when using the Lucas Formula but try not to introduce them until you have perfected your setup. You need to make sure that there are no deficiencies present and have a good understanding of how your plants like to be fed before introducing additives into the picture. One should rather focus on getting a good quality genetics, have enough light and control the temperature from the very beginning rather than compensating with additives.

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Information sourced from

How to grow with 3 Part Nutrients such as General Hydroponics & Terra Aquatica?

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Tank - November 1, 2021

So honestly dose maxibloom seem to be the best cost efficient way to increase your yeild?

Bebo - November 2, 2019

Lucas + hempy = the easiest way to grow. I tried soil and my plants struggled to grow. Now with Lucas and Hempy I have way less issues. It’s just easier.

Rambo69 - November 2, 2019

Hi the top formula the 8-16 is that for a soil grow thanks ..

Royce - August 1, 2019


So the formula above will be the same measurements for the EHG’s 3 part System. That being 8ml’s of Micro and 16ml’s of Bloom to 3.78 litres.

Blair Mckinnon - August 1, 2019

When using G h nutrients does callmag aroot booster give a better yield. I would like to try the lucas formula. Does the additives give this method a bigger yield

Slow Boat - November 11, 2018


So the formula above will be the same measurements for the EHG’s 3 part System. That being 8ml’s of Micro and 16ml’s of Bloom to 3.78 litres.

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