Purple Bud

Ideal Grow Room Conditions For Kick-ass Hydroponics Marijuana

What you do or don’t do in your hydroponics marijuana grow room makes all the difference in yield and potency.

That’s why we’re giving you this exclusive description of the specific ideal conditions for growing marijuana indoors.

These conditions are time-tested by the largest commercial marijuana growers and the most serious home connoisseur marijuana growers in Colorado, Washington, California and other legal cannabis states.

The closer you get to making your marijuana grow room have these conditions, the closer you get to marijuana maximum yield!

TEMPERATURE RANGE: During lights-on cycle, 72-76 degrees Fahrenheit (F).

Maximum operating temperature is influenced by whether or not you are adding C02 to your hydroponics grow room. Ideal day cycle growing temperature without C02 augmentation: 74F.

Ideal day cycle temperature with maximum C02 augmentation at 1100 ppm C02: 84F.

During lights-off cycle, between 66-70F. Watch your cannabis strains to see if temperature stress is affecting them.

Some varieties of marijuana need slight adjustments to day and night temperatures.

ROOT ZONE TEMPERATURE: 67-68F. If you’re growing in basements or cement slabs, don’t put pots directly on the floor, as this can cool the root zone too much, especially in colder months.

WATER/NUTRIENT SOLUTION TEMPERATURE: 66-68F. Warmer than ideal temperatures in nutrients solutions contributes to growth of harmful organisms in hydroponics reservoirs or can slow root function and deter root growth.

You may have to add a hydroponics chiller to cool nutrients water if your grow room is too hot.

In rare cases, you may have to add something like an aquarium heater if your nutrients water is too cold, because cold root zones harm roots and slow growth.

GROW ROOM HUMIDITY: 51-61% during vegetative phase; 51 to 59% during flowering.

Excess humidity creates conditions that allow mold, powdery mildew, and other harmful organisms to flourish, which can destroy your buds.

It also drowns your leaves in air-borne moisture, which interferes with leaf “breathing.”

Insufficient humidity means your marijuana leaves evaporate too much water.

This strains your marijuana roots (because they have to intake more water) and could create other problems.

LIGHT CYCLES: Vegetative Growth: 18 hours on, 6 hours off. Floral triggering and growth: 12 hours on, 12 hours off. Note that for auto-flowering marijuana you run 18-24 hours of light from start to finish.


For clones and seedlings- T-5 high-output fluorescent lighting or LED lighting.

For vegetative growth of established plants, depending on the size of your grow room and whether you’re using photoperiod marijuana or autoflowering, you can run LEDs, plasma, T5s or metal halide (MH).

Lighting for Marijuana Bloom Phase: High Pressure Sodium/Metal Halide in combination, with more HPS than MH.

High quality LED lights such as Lush Lighting LED grow lights.

You might choose non-HID lighting , especially a large-size, high-output T-5, when you have very limited space, lacking heat removal and/or air conditinoing, and with SCROG, Sea of Green, chambers, autoflowering marijuana.

LIGHT COVERAGE: For stationary lights, One 400 watt HID bulb provides adequate light for 8-9 square feet of space.

A 1000-watt light provides adequate light for 16-25 square feet of space in a hydroponics marijuana grow room.

The use of light movers extends these coverage areas.

LIGHT REFLECTION: Easy Grow reflective materials, Mylar, white glossy poly plastic or similar materials on all marijuana grow room walls.

Aluminum foil, mirrors, and white paint do not have adequate degrees of reflectivity.

DISTANCE OF PLANT TOPS TO LIGHTS:  These distances are for established plants with well-developed root systems.

Metal Halide and High Pressure Sodium bulbs, if not separated from plants by glass or in cooled hoods should be at least 28 inches feet from top of plant to bottom of light.

Double-ended bulbs should be at least 32 inches from the canopy, unless they’re in cooled fixtures.

Fluorescent lights can be eight inches from hydroponics marijuana plant tops.

LEDs can be 15-25 inches from hydroponics marijuana tops as long as the plants have adequate root systems.

Glass-shielded and/or cooled MH/HPS: 18 inches from plant tops.

Double-ended HID bulbs without cooling should be 30 inches or more from your canopy.

These guidelines are approximate. Hold your hand under the light where your leaves are. If your hand feels like it’s too hot, your leaves are too hot, so move the light higher.

STERILE GROW MEDIA: Grodan Rockwool, coco coir, lava rocks, vermiculite, perlite, clay pellets, water culture.

Note that I do not include soil. Why? Because soil cannot be totally controlled.

ATMOSPHERIC REQUIREMENTS: Growing medical marijuana indoors requires that your marijuana plants get large amounts of oxygen, including in the root zone.

They also need large amounts of carbon dioxide (C02), especially at underside of leaves.

Ideal total ambient C02 in your marijuana grow op should be between 900-1600 parts per million during lights-on cycle.

Natural C02 levels are approximately 387 ppm.

Your C02 emitter should be timed in relation to exhaust fan so that C02 is not sucked out of room.

Don’t add C02 during lights-off cycle.

AIR CIRCULATION (INTERNAL): Circulation by at least one medium size oscillating fan for any size grow space, no matter how small.

For larger hydroponics marijuana grow spaces, at least one medium size oscillating fan for every 1000-watt light.

You should be able to feel and “see” air movement in your grow space at plant level so that all plants’ leaves are in a gently moving ocean of fan-driven air.

AIR EXCHANGE: Install exhaust fans sufficient to totally exchange all air in grow space every 1-3 minutes.

Exhaust fans must be timed relevant to C02 augmentation to avoid removing augmented C02 from your hydroponics marijuana grow room.

IDEAL Ph OF GROW MEDIA AND NUTRIENT SOLUTION/WATER: Between 5.7 and 6.1. IDEAL pH OF SOIL: 6.5. Use pH Perfect base nutrients so you eliminate worries about pH.

IDEAL PPM (parts per million) OF HYDROPONICS NUTRIENTS SOLUTION: Nutrients intensity varies widely and you have to watch your plants closely because nutrient burn is an epidemic in our marijuana growing community, especially during bloom phase.

In general with established marijuana plants, start by running 1/4 to 1/2 of the manufacturer’s recommended nutrients dose and go up from there.

If you’re running more than 1300 ppm, and especially if you don’t flush periodically, you may toxify your root zone and marijuana plants with excess nutrients salts.

IDEAL WATER: Rainwater, or reverse osmosis water.

Tapwater and well water are almost always polluted in ways that will harm your root zone and marijuana plants.

IDEAL SECURITY PROTECTION: Filtered air intake and outflow.

No pets, debris or other polluters in the grow room.

Don’t tell anybody you grow marijuana.

Isolate your plants from mold and mildew spores and other vectors.

Now that you know the ideal conditions for growing medical marijuana indoors, there’s one other thing for you to know: having a sealed grow room (otherwise known as Controlled Environment Agriculture, or CEA), is going to give you the best chance to create the ideal hydroponics conditions for growing marijuana indoors.

If your marijuana plants are having problems, the causes could be genetics, your grow room environment, their root zone material, and what you’re feeding them.

Many marijuana growers are not providing ideal indoor grow room conditions, and they’re losing out on maximum yield per watt.

Don’t be a marijuana plant abuser.

Establish these ideal conditions in your grow op, and get more weight and THC from your marijuana plants.

You and your hydroponics marijuana plants are worth the investment.

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