Growing Cannabis Indoors: The Fast Way In Hydroponics

Growing your first crop with hydroponics

A brave choice for your first indoor grow! This is the absolute fastest way to grow indoors and will result in a fast harvest. However, expect to work for this. While you can leave the plant alone for a week or so, you must replace nutrients regularly, and you need a lot more equipment to get started. Hydro also doesn’t have the same buffers that soil does and does not forgive mistakes like potting mix.

A note on your first indoor grow

Using some rigid foam, hardware store ducting, and epoxy, you can easily build a window exhaust

First off, If you want the 101 class on indoor gardening, check out our intro to indoor growing series. You need a few things, but the most difficult to deal with is ventilation. You see, cannabis has a very pronounced smell. I describe it as “overpowering for any indoor area”. So, you need to make a device to vent the smell outside and optionally scrub the smell from the exhaust. So, your first order of business is to find a place where you put the plant where you can attach a vent to the outdoors. I recommend making a vent out of some rigid foam and using epoxy to attach some ducting to it. It’s cheap and you can bang out a vent in an hour.

What you need

OK, now that you have your ventilation worked out, it’s time to assemble your materials. You need:

That said, let’s gather our parts list:

  • A place to grow next to power, and a place to vent
  • A grow enclosure. You can use a tent , cabinet, or a cardboard box. Doesn’t matter. Make sure the inside is reflective or bright white, and you can get power in, has a way to take in air and exhaust it. It needs to slightly taller than the size you want to grow your plant. Stick to a 2’x2’x4′ for starting if you’re going to make something. Make sure the bottom is waterproof.
  • A light. You should get an HLG 135 for this. If you can’t afford one, the Roleado 300W will work, but they are far less efficient… Granted, they are also 1/3 the price.
  • A light timer.
  • Your ventilation: Fan, ducting, exhaust, and optional carbon filter. A fan speed controller is also nice, but not 100% needed. Kits are available to make this easier.
  • Thermometer and humidity sensor.
  • A small fan
  • A bubble bucket kit. We like the HTG Bubble Boy kit, as it’s a great value for a small indoor grow.
  • The General Hydroponics starter kit.
  • Optionally, a TDS meter and pH tester.

Setting up

Let’s get this grow going:

  • Build your bubble bucket. You can follow our instructions, or use the instructions that came with your kit.
  • Put your seedling in the net pot on top.
  • Put 2 gallons of water in the bucket, and mark that line. Mix the nutrients in the water, (2.5ml/Gal each of FloraMicro/Grow/Bloom) test pH, and adjust as needed to get it close to 5.8. Remember that you need to dilute the pH adjuster about 50:1 or you’ll start precipitating things out of the solution.
  • Put the net cup on top and adjust the water line so it will reach the roots of the plant. You can dilute the mixture with more water, or add some clean, plastic soda bottles filled with water to raise the level.
  • Add the cleaned seedling or clone, and surround it with the expanded clay balls or whichever medium you are using.
  • Finish installing the air pump and stones in the water.

Now you’ve got a plant in a bubble bucket, ready to grow. Your next step is to setup your grow area.

  • Setup your tent, modify your cabinet, or cut the right holes in your cardboard box for power and ventilation.
  • Put your plant in it.
  • Adjust your fan to get a light sway on your plant. No fan will lead to slower growth, and a weak plant.
  • Adjust your light about 18″ above the plant. Set your timer to keep the light on for 18 hours a day.
  • Setup ventilation. Don’t forget to have an inlet opening, and setup any filter you can on it.

Vegetative Growth Care

Indoor cannabis grow image
3’x3’x Tent with two plants

Once your environment is good, you’ll grow your plant to about 1/3 the final size you want it. This first phase is called vegetative growth and it represent the phase where you plant tries to grow large so it has places to put flowers. This should take 3-4 weeks in a 2x2x4 tent, but could be a week if your space is small.

You need to do the following to care for your plant:

  • Check your plant daily. Look for discolorations, pests, and off-smells.
  • Check the air pump and make sure it’s bubbling the water.
  • Test the nutrient pH every couple of days and adjust to keep it near 5.8.
  • Check your bucket for scum buildup. If that happens, immediately  clean the bucket and refill with nutrient solution. You will want to add 3ml/Gal of 29% hydrogen peroxide as well.
  • Make sure the ventilation and lights are working.
  • Keep the temperature below 80, and the humidity below 80%.
  • Raise the light to keep it about 18″ above the plant’s top-most part.
  • Watch out for the plant turning deep green, which means over fertilization. General paleness indicates under-fertilization. Spots, necrosis, black patches indicate pH problems.

Flowering Care

Once it’s about 1/3 the final size you can have, time to flip for flower. Set your light timer for a 12-hour on-time. You will now maintain your plant differently:

  • Perform the same tests you did during vegetative growth, except keep the light 12″ above the plant.
  • Keep the temp below 80, and the humidity around 50%. Anything over 70% is a high risk for mold.
  • Watch out for the plant turning deep green, which means over fertilization. General paleness indicates under-fertilization. Spots, necrosis, black patches indicate pH problems.
  • Your plant will be ready to harvest in about 8-12 weeks.

The nutrient regiment for the GH kit has a lot of rows to perfectly optimize things. You can certainly follow that, but the rule of thumb for beginner grows is to use:

Seedlings (less than a foot tall): 2.5ml/gal of the 3
Veg stage (1 foot tall until you flip to flower): 5ml/gal FloraMicro, 10 ml/gal FloraGro and 5ml/gal FloraBloom
Early Flowering (from flip to about 3 weeks into flower): 7.5ml/gal FloraMicro, 7.5ml/gal FloraGro and 10/gal FloraBloom
Late flowering (hopefully most of the grow): 10ml/gal FloraMicro, 5ml/gal FloraGro and 15ml/gal FloraBloom.
Flush (last week of the grow): FloraKleen at 20ml/gal for 7 days

Adding the secondary nutrients at their nominal values is a good call as well. Most importantly are RapidStart in the first few weeks, and Liquid KoolBloom in the flowering stage. CalMagic is required if you’re using water with a very low calcium content (your local water report will tell you, but if you have hard water with lots of white build-up, you’re all set).


  • Your plant might need support as it gets larger. It’s much easier to plan for this early rather than rigging up a hack later in life. Get some horticultural netting and attach to the grow area right above your small plant. This is called the ScrOG net (Screen Of Green) and as the plant grow through the openings, it will be supported.
  • Get a second bucket so you can just lift the plant and swap buckets, rather than having to deal with cleaning your only viable bucket.
  • Check pH often. It accounts for about 80% of plant problems in deep water culture. The rest are mostly bacteria in the water, or the nutrient mix is off.
  • Keep a humidity and temp probe in the grow chamber. Do your best to prevent mold by keeping humidity near 50% and keep temperatures in the 60°F-80°F range.

When should you harvest

Trichomes are the little “hairs” on the plant, and they are the best indication of how ready the plant is. Check the ones coming off the buds (not the sugar leaves). If you have an inspection microscope, you can take a peek at them on the buds to see if it’s time. You should harvest when most of the trichs have turned from clear to milky and before too many turn amber.

Look for milky trichomes and a little amber


Buds on the bottom screen and the light rack doing double duty as a drying line

There are two schools of thought on this. You can either cut the plant down, dry it, and then trim it, or pre-trim and dry. Both work acceptably. I’ve found that pre-trimming is best if humidity is high during drying. In either case, I would highly recommend a quick trim of fan leaves before you hang your plant to dry. The fan leaves and stems are not very useful after harvest and can be discarded or composted.

Chop your plant down in the largest portions your drying system will accept. You are going to want to hang the branches in a dark place with airflow and about 50% humidity. Alternatively, you can use hanging nets designed for drying to do this part. In this case, Cut the plant into handful-sized pieces to dry and spread them out on the net.

After 4-days to a week, they will be dry and you can then begin the final trim. Get yourself a good movie or some tunes, rubber gloves, comfortable scissors, and relax while you cut off every sugar leaf to the best of your ability. This is easy, but time consuming. Make sure to trim over a bin to catch it. Those leaves are covered in trichomes and therefore THC. You can make extracts from that pretty easily. Also, all the residue on your gloves and scissors is basically hash, so… feel free to dip it all in grain alcohol to extract it and do what you will with it.


The last part is to cure your crop. Now that you trimmed everything, break them in to smaller pieces and put them in sealed jars. You want smaller jars so that if a jar gets mold or goes bad, you don’t lose the whole crop.

You will let them sit in these jars for about a month. Open them once every few days to release moisture. If you’re in a dry place, you might want to had some humidification packets to the jars. They prevent the buds from getting too dry.


Now you should have a good starting point on your journey. Make sure you look through our articles that might be a good resource for you, like:

If you have any questions, have any suggestions for what you’d like to see in future articles, or want to have us help you in your home grow, contact us and we’ll be happy to help out.

6 years ago

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