Growing Indoors With Coco Coir

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Growing with Coco Coir — Indoors — in a 4x2ft Tent

Friendly Aussie Buds are using 2x5gal (7.5x19L) smart pots.

Coco as a Unique Medium

Coco Coir is a mostly inert medium, containing cation exchange sites that naturally contain K and Na. These sites will preferentially suck up Ca and Mg, releasing K and Na. Removing the Na and K is known as ‘buffering’.

Natural, unwashed coco coir contains coco fibre (good large fibres), and coco peat (bad, dusty fibres). Coco requires washing before use to remove coco peat, and also before reuse due to coco fibre degradation, which creates more coco peat over each grow.

The medium has a moderate ion exchange capacity, and is prone to salt build-up without regular checks. You will need to be providing balanced nutrition to your plant and medium at all times, with additional CaMg to buffer the coco — both before use, and during the grow — ****as the coco fibres degrade.

At 100% medium saturation, properly prepared coco should still able to provide ideal root oxygenation to a mature root system, when mixed appropriately with perlite or ‘coco chips’.

You must always keep your entire coco:perlite mix visibly moist in order for nutrients to be dispersed. Coco has a wide angle of nutrient solution wicking — ****or ‘dispersion throughout medium’, when wet… but this dispersion angle becomes narrow when dry. Coco can be difficult to remoisten once dry.

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You can use anywhere between a 50:50 coco:perlite mix, up to a 100% coco mix. Consider external VPD conditions and your intended watering method, when choosing upon a mix. The less perlite, the more moist the root environment becomes; meaning less regular watering is required. 70:30 coco:perlite or 50:50 coco:chip are very common and reliable mixes. Coco fibres with coco chips can aerate similarly to a coco:perlite solution.

Protip: Use an additional inch of perlite on the top and bottom layers.

High-Frequency Fertigation

High-Frequency Fertigation — also known as nutrient irrigation — is recommended in order to keep your medium saturation level between 90-100% throughout flowering stage.

Nutrient Feedings are recommended with every feed. Weekly flushes are optional — they help to refresh nutrient pathways in coco coir (+/- Crystal clear or Ecozen).

Try to schedule your feeds with an autotimer/pump during flowering stage. 5% of the medium volume in nutrient solution at each feeding achieves 10-20% of this feed as runoff.

For a 5 gallon container (~19L), you want to feed 1L per feeding and have 100-200mL of runoff from that plant, following the feed. Time the number of feeds per day based on how regularly you need to feed 1L to cause 100-200mL average runoff — during ‘lights on’.

It is possible to hand-water coco in a larger container, and/or with less perlite. For best results, it’s recommended you hand-feed every second day to twice-daily in 7-10gal (rather than 5gal) containers.

Expensive ‘Coco Bags’ vs. Cheap ‘Coco Bricks’

Cheap coco bricks will have high Ka and Na (salt) levels, due to a lack of pre-buffering. They will also contain a high level of coco peat (or ‘coco dust’), which will need to be washed out.

Use of Calimagic (or any CaMg, and a perforated 1/8” kitchen strainer) is recommended for buffering and washing unprepared coco.

Tap water + Calimagic@ 2mL/L is sufficient for buffering soak. Double overnight soaks for 8 hrs at a time recommended before use, after first washing the coco of coco peat.

Overall, coco coir needs extra CaMg and less K.

Without correct buffering, both before use and during the grow, Calcium and Magnesium deficiencies are common.

Without correct washing before use and/or perlite ammendment, overwatering is common. This is because coco peat, a dust-like degradation product of coco fibre, does not aerate nearly as well as coco fibre

ReusingCoco Coir

To reuse coco coir for multiple grows, washing with each reuse is essential; this is to wash away coco peat that will have formed over the grow, as the larger coco fibres degrade.

Works best with high frequency fertigation… +/- an optional regular flush by hand, or inbetween reservoir changes.

Coco coir requires more feeding and measuring of salt levels, compared to soil… but it has better medium aeration, and relatively environmentally friendly.

Coco Vs. DWC

Okay, so DWC’s growth is faster; and coco coir can require more nutrient input.

But… consider that getting started with Coco Coir is much less cost and labor intensive. Coco is also more mobile in a container during vegetative stages.Coco can act as a buffer against environmental conditions and other mistakes… whereas *issues* can happen suddenly and at any time in a hydroponic setup.

Coco Vs. Soil

You can lovingly overwater a plant growing in soil – to death – pretty easily. It’s not so easy to do that in Coco. Coco requires more day to day labor than soil, however – like checking pH and EC.

It’s also pretty expensive to maintain an optimal environment in coco, compared to a good soil… which just needs water and occasional/cheaper amendments.

Recommended for 4×2 Tent

Extraction Fan/Controller/Carbon Filter
Cheap carbon filters produce much worse results and need much faster replacing… cheap fans also don’t create good pressure through a carbon filter.
200-300W LED lighting + cheap auto timer to set 18/6, 12/12 cycles
30-50L nutrient reservoir/pump/tubing/feeder rings/auto timer/recirculating pump
50L of your medium – Coco + perlite and/or coco chip
Plant stands + drainage trays
1-2 plants, 2x 5gal fabric pots
Recirculating/Oscillating fans (want leaves lightly dancing in the breeze) x2
EC pen/pH drops
Spray bottle with adjustable nozzle for weekly foliar spray

Water Quality

Ideally, you want tap water between 0 and 0.6 EC, without any chloramine added to the water supply. You can have your house water-tested at various places. You should be able to find out online whether you have chlorine or chloramine added. Chlorine can be left in an open container to gas off overnight.

A sediment and carbon filter is a fairly cheap way to improve water quality; otherwise, an RO (Reverse Osmosis) filter might be a better option. My water ATM is 1.2 EC for with chlorine added. I can either mix tap water to RO water in a 1:2 ratio or just use pure RO water.

Chloramine can be removed with catalytic carbon filter/sediment filter combos… but with particularly high EC water, and/or water with chloramine, RO filtration becomes a good option.

A lot of the EC value of the water can be Ca in the form of limescale among other micronutrients, which, with various amino acids and bio stimulants added, can be made readily available to the plant. The lower EC your water, the more CaMg you can add as a base to your nutrient solution

With 0EC water, I add 0.15-0.3EC worth of CaMg (0.25 to 0.5mL/L Calimagic) throughout the grow. In general, Calcium use builds to a maximum in early to mid flower as plant matter growth is at its highest, then drops back to nothing for the last 2-3 weeks of flower.

In coco, additional CaMg is required, as coco fibres degrade and expose new cation exchange sites over the course of the grow. This tends to happen most in vegetative stages, as roots spread throughout new containers.

Protip: You can compensate for dry conditions with increased coco to perlite ratio and for humid conditions with increased perlite to coco ratio.

Main ‘Weak Links’


Maximum grams to expect is always relative to watts pulled from the wall.

HPS ~ 1/W yield max
Blurple LED 1g/W yield max
CMH ~ 1.5g/w yield max
LED ~ 2g/W yield max
Some LED light options:
  • Chinese knockoff (ie kingbrite) QBs are pretty unbeatable for price to performance. 3500k spectrum w/ added 660nm cree currently the most recommended spectrum for start to finish and flowering, recommend 240/320W kits.
  • 260W XL HLG rspec. Dimmable from 90W up. Australian driver model only hits 240W, international version hits 280W (need to wire up additional plug converter).
  • 2-3 x 200W UFO lights (100w actual) with mixed 3k, 5k Samsung diodes + 660nm orsam reds (plenty of different UFO models exist, but I’d only recommend this one).
  • Spyder, Gavita, ChilliLED, HLG saber bar lights: best penetration with bar setup, but expensive.

The less efficient the light, the more heat it is adding to your environment. With HID, radiant heat is higher increasing leaf transpiration. HID/HPS lighting can be helpful in cold damp conditions, and harmful in hot, dry conditions. HID is also often lower in short term cost, but higher in long term cost, considering bulb replacements and extra power use relative to LED.

CHM provides the most complete spectrum relative to the sun, and it is said to grow some of the strongest, most colourful and tasty indoor flowers.

Horizontal Space

Expect most strains to yield 400-600g/m2.

A lot of F1s can have a large range of phenotypical expression. Generally aim for 400g/m2, which equates to 300g or 10+ zips from a 4x2ft horizontal area. Growing from clone can be a better point of reference for how well you are doing things (if available).

240-280W LED flowers a 4x2ft space perfectly, as does 315W CHM and a 400-600W HPS. That’ll let you grow start to finish with the best of the best. Blurples aren’t great for flowering; but they still make good vege lights… for the price.

Environmental Conditions

Expect closer to ¼ to ½ optimal yield with bad environmental conditions, such as:

Salt buildup and antagonism of minerals due to buildup and/or pH swing during flower.
Poor Calcium uptake.
Incorrect VPD.
Poor airflow and/or air exchange (lowered CO2 absorption by plants leaves).
Replace air in your tent every few minutes or more and have leaves lightly dancing in a breeze. For a 4x2x6ft tent (48 cubic feet), this means getting a fan that is > 100 CFM.
Carbon filter attached will reduce a cheap fan’s effectiveness by around 20%. Correct carbon dioxide supplementation can optimise results in a sealed environment.
Poor light penetration resulting from bad plant training leads to lower quality larfy (airy) bud in the lower part of the plant.
Incorrect soil moisture conditions will stunt root growth and microbial life.
Pathogens and pests can cause significant stress and loss of yield.
Hot conditions: you can compensate with a larger pot size, a water cooler in the nutrient reservoir, more regular feeds, ice blocks left on the topsoil, decreasing light intensity, and increasing environmental humidity closer to VPD range.
For cold conditions: HID lighting, nutrient reservoir temperature controllers, and heat mats wrapped around the pot/s on a temperature controller can help

What Can I Expect With Yield?

This is all assuming ideal conditions.

For a 4x2ft tent (0.75m squared horizontal area), if you are aiming to grow a lb (~450g), equating to an end yield of 600g/m2, you’ll need a supply of:

225W (240-280W recommended) of quantum board LED, or
450W (400 or 600W dimmed) of HPS, or
300W (315W) of CMH

Auto-Watering Setup for Indoor Coco

Automation can greatly reduce labor associated with mixing up regular feeds or hand-watering plants daily. For a much more relaxed, and potentially cheaper approach to growing, soils can allow for much less frequent watering, and less feeding of expensive products.
Parts needed for 2 plants in 3-7 gal pots:
1x Submersible Pump 500-1500L/hr, ~5-15W power use – $15-40 (go to a good aquarium store)
1x Programmable Second Timer to hook pump up to for feeds – $30-45
1x Length of 13mm Flexible Irrigation Tubing – $2/metre
1x 13mm T-piece Connector (or a 19mm to 13mm t piece for the 1500L/hr pump) – $1
1x Packet of Cable Ties – $2
2x Feeder Rings*
(the resistance in these and how many your running from one pump will determine what size pump you need) – $5-10
*You can get fancy sprinkler rings and stuff that needs a lot more water pressure to come out evenly. They do soak the coco a little better.

All up, about ~ $90, taking about 5 minutes to physically setup, and another 5 minutes to program the timer. Although, you often need to do a fair bit of tinkering to dial-feed times.

You are aiming for 5-20% runoff per day (overall) for each plant – relative to how much you’re feeding it per day, of course. Always measure runoff EC. If it’s creeping up: flush the medium (a coco flush solution is recommended), decrease the EC of your nutrient reservoir and/or increase feed volume per day.

Bird’s Eye View of Pump Setup

It helps to cable tie the setup at the T-Piece to keep everything nice and tidy.




{Pump} = Pump in Reservoir Bucket
=== = 13-19mm tubing
| = T-piece to feed to both plants at once
(13 to 13mm or 19 to 13mm T-Piece)

0 = Feeder Rings/Plant Pot

Social Considerations

A carbon filter and/or air purifier for flowering is recommended. negative pressure extraction tent sealed to the outside is also a good move. Be stealthy, and kind to your neighbours.

Cheap fans will lose significant power when attached to a carbon filter, andcheap carbon filters are a lot less effective than good ones. Don’t skimp where smell can be an issue

Also: try to tend to some legitimate plants – particularly tomatoes and herbs if possible, to explain shit lying around.

Perlite is not very stealthy to dispose of. Coco chip mixes blend into the garden much better. Rewashing and re-buffering is possible with separated coco brick:perlite mixes, indefinitely. Add a little extra coco over time as coco fibre breaks down and you wash off coco peat

Common Beginner Mistakes

Over-Loving Your Plant

Too many nutrients, water, etc.. It is still very possible to overwater and stunt young coco plants in bigger pots in particular and/or with badly prepared coco:perlite mix

Blindly Following Guides

Like my shitty ones… without listening to what your plant is trying to tell you.

Growing a Bagseed – or Poorly Tested Seed

…and not knowing if it was your fault or not, if it hermies.

Not Reading Runoff EC/pH Regularly or Properly

You’re prone to letting salts buildup in the medium, if you do this – for any hydro grow, you will need to be right on top of this at all times. Poor pH readings or faulty calibrations can also lead to mistakes.



Applying a Combined PK Boost – from start to end of flower

This can lead to too much K building up in the medium during early flowering stage. This leads to P, Mg and Ca being locked out early in flower, when it is needed most. This greatly reduces yields.

Using an airstone in a reservoir with organics.

A recirculating pump is best to keep your nutrient mix fresh for as long as possible.

Finally, mix up your nutrients in the correct order and use equal amounts of A+B solution.

Common Coco Problems

coco coir

  • Acidic pH from excessive pH down can cause spots all over leaves on new growth.
  • Alkaline pH from inadequate pH downing, salt buildup or not checking nutrient reservoir pH enough can lead to interveinal dechlorosis on the newest growth.
  • With appropriate use of microbes and biostimulant chelates, the range of acceptable pH for nutrient uptake is increased.
    • Rapid/major up or downward pH swings can do more harm than good, as the root environment can adapt to slow pH changes OK
  • pH will naturally move to a neutral 7 pH over time due to oxidation. 24hrly pHing of nutrient reservoir back to 6 pH is recommended. Omission of certain organics can lead to a much more stable reservoir pH if you are going to be away for a few days
  • Leaf burn can result from high temperature, low humidity and/or a high salt environment.
    • Excessive use of nitrate salts and inadequate calcium + biostimulant use can lead to plants more prone to leaf burn and disease due to reduced calcium uptake and larger plant cells with thinner cell walls
  • Downwards nitrogen toxicity – leaf claw tips are a classic sign of excessive nitrate levels
  • When coco is moist, it has a wide angle of drainage; meaning water and nutrients are very effectively wicked through the entire medium from a point source.
    • When it dries out, coco becomes very narrow in its drainage angle, meaning nutrient solution tends to fall straight through without wetting the coco properly… and without washing away unused salts, or providing new nutrition effectively.
  • Leaves falling off the plant at a rapid rate in flower can be due to an unchecked salt buildup, or from flushing too soon during the final stages of flowering.
  • Feeding a high-EC PK flower booster from start to finish of flower can significantly hinder yields. K is needed very little early on in flower and buildup locks out CaMg and N, which are all needed at high levels early in flower. This is mainly due to Ca lockout, as Ca is an immobile nutrient. This means that deficiency causes immediate issues.

Contributions from Mick Hardwood. Edited by Mitch.


Author: Mitch

Mitch Keys is a young writer from Brisbane, Australia unfolding in a dynamic process of becoming (like everyone else, so don’t go thinking he’s special or anything). He likes being alive.

Mitch Keys is a young writer from Brisbane, Australia unfolding in a dynamic process of becoming (like everyone else, so don’t go thinking he’s special or anything). He likes being alive.
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