Sunday, January 29, 2012

The Importance of Darkness

And why I don't recommend the 24/0 Light's on schedule...

Even if you're growing indoors, with a Hydroponic and HID light system, it's still important to practice the basic rules of nature. Where there is a Yin there is a Yang, and that is specifically true in nature. Plants need certain periods of darkness just as they need certain periods of light depending on the season. In the wild, plants will grow according to the "lights on-light's off" cycle. So for example if it is spring/summer(longer days, shorter nights) then the plant will take notice and use this extra light to grow more foliage. When the plant begins to notice the change into autumn/winter(shorter days, longer nights) then it will begin to end it's vegetative growth and begin producing flowers or fruit.

So what do plant's do in the dark?
During the bloom state they develop the necessary hormones in order to produce flowers and vegetables. During the seedling/vegetative state they use the darkness to grow roots and longer stems. While plants are capable of growing roots while the lights are on, they prefer the cover of darkness, and most of their roots will grow during dark periods. Ask any grower, farmer, even scientist, and they will tell you that in order to grow a successful plant you must first start with a successful root system. So by allowing your plant extended periods of darkness you will extend your roots/stems which will produce lush green foliage. However, too much darkness can cause your plants to "stretch" (stems growing too fast in order to reach light) so balance is the key; Yin/Yang

Here you can see the development of the root system over time


So why wouldn't the 24/0 Light Schedule work?
It's not so much that it doesn't work, it's just that the motivation behind it is ironic. The reason why growers leave the lights on for 24 hours is so that they will promote more growth. However, without darkness, or extended root/stem growth, they are forcing the plant to grow more foliage. While it seems like a good idea you are actually stressing your plant, and leaving it weak at the base making it more vulnerable to disease/pest. It's like a human taking steroids and only working out his upper body; strong muscular definition above, and weak chicken legs below.

So in conclusion, it's better to go with the flow of mother nature than against her. I personally stick to the 16/8 Light cycle for Seedlings (more darkness for more roots), and the 18/6 Light cycle for the Vegetative state (to simulate the longer days of summer).

Thursday, January 26, 2012

One man's junk is another plant's treasure

Dirty Aquarium Water:
Contains: Nitrate & Nitrite which breaks down into Nitrogen
Base pH: Depends on your Aquarium
Best For: All Plants during the Vegetative Stage

Alot of people get mixed up about this one and is why they usually give up in the beginning. While dirty Aquarium water does contain traces of Nitrogen, it is dissolved (or eaten) by other beneficial bacteria in your tank. This bacteria begins after a proper tank cycling otherwise your fish would die of NO2/3 poisoning. By watering your plants with this dirty water, you are building up the levels of Nitrate(NO2) and Nitrite(NO3) in your soil which will begin to slowly break it down into Nitrogen over time. Once this happens the results will be instantly rewarding, and your plants can even be used to directly filter the dirty water in your Aquarium. Read About Aquaponics


Used Coffee Grounds:
Contains: Nitrogen, Magnesium, and small traces of Potassium
Base pH: Acidic (low)
Best For: Tomatoes, Blueberries, Peppers, Potatoes, and all acidic plants


Gently sprinkle dried up used coffee grounds around the base of the topsoil, or pre-mix into soil before transplanting or sowing. Since coffee grounds have a low (acidic) pH, be careful not too add too much otherwise it will drop your soil's pH level as well. Use 2 cups or less of used coffee grounds per every gallon of soil to avoid low pH issues. 



Discarded Egg Shells:
Contains: Calcium and small traces of Nitrogen
Base pH: Neutral
Best For: All Plants, especially during seedling/vegetative stage
*Warning - Fermented eggshells smell rotten and can quickly stink up the house

For seedlings, crush and place broken shells into any water container (which has a lid), and allow the eggs to ferment in water for 48-72 hours. Water your seedlings around the base (but not directly on the leaves) for a quick calcium boost. After transplanting, gently sprinkle dried crushed shells around the base of the soil so that they will get wet during waterings. This will release a consistent source of calcium over time along with your water/eggshell boost.



Fireplace or Wood Ash:
Contains: Potassium and traces of Calcium Carbonate
Base pH: Alkaline (high)
Best For: Plants which require high amounts of Potassium and can tolerate a higher pH.

Wood ash is a natural source for Potassium, however stay away from self-igniting firewood (such as Duraflame etc.) because they contain chemicals which can hurt your plant. Furthermore, wood ash is high in pH value so be careful not too add too much to your soil mixture or topsoil base. Use roughly 1 cup or less per every gallon of soil. Start off small and gradually work your way up to prevent shock, and if you see your plant's health start to diminish then reduce the amount fed.


So can I use all of these 4 ingredients together? 
Yes, and in fact they actually work better this way. If you're growing organically, then you've probably already figured out that you need a mixture of multiple types of organic fertilizer in order to provide sufficient and lasting nutrients. No single organic fertilizer is going to be enough for your garden, unless you buy a pre-mixed bag which was engineered and proven to provide the right amount of nutrients. Call me cheap, but If I don't have to buy fertilizer, and can get if for free out of my trashbag, then I would rather dig through the trash. Here's what I do with these 4 items on this page:
1. Premix my soil & perlite like I would usually do with any plants
2. Sprinkle into the soil mix 2-4 cups of dried used coffee grounds
3. Sprinkle into the soil mix 1-2 cups of crushed egg shells
4. Sprinkle into the soil mix 1-2 cups of wood ash
5. Water heavily, test pH, and allow to completely dry before using

The reason why I water my soil and let it dry is because it will begin the breakdown process of the egg shells, coffee grounds, and wood ash before I use the mix for transplanting/sowing. In addition, the water I use to wet my soil is dirty aquarium water. Furthermore, always make sure to test your pH levels as well, and you can use more wood ash to raise pH, or more coffee grounds to bring it back down.

Tuesday, January 24, 2012

Why I can't start a successful plant with Rockwool

Alot of new indoor gardeners who are successful outdoor gardeners, usually run into this problem the first time they use Rockwool to sprout seedlings. While Rockwool is a perfect medium for clones to develop a root system, it is not recommended for sprouting seedlings.



Rockwool is basically a sponge with a nuetral pH. It contains no beneficial bacteria, micro-nutrients, or natural buffers which seedlings need in order to survive onto the vegetative state. While it is possible to successfully sprout seedlings in Rockwool, they are better designed to promote root growth from a clone or cutting.

Below are a few common mistakes which usually lead to the seedling's death:

  • Over-watering; constantly keeping the Rockwool moist, or allowing it to sit directly in water.
  • Using the Rockwool directly out of the package without flushing it first.
  • Using large cubes (3" or bigger) for tiny seedlings
  • Not checking the pH: allowing it to become to acidic or too alkaline


If you wish to start (or germinate) your seedlings in Rockwool cubes, then chose small plugs of 1-1.5" in diameter. This will allow the root system to quickly emerge through the cube so you can transplant it into Hydroton or Soiless mediums. This will give the roots access to the beneficial bacteria and/or nutrients introduced through your Hydroponic system or Soiless mix. Furthermore, make sure you flush your Rockwool cubes with water (or even h202), and never allow your cube to sit directly in water or to retain excess water (squeeze the cube like a sponge to remove excess water).

Transplant your Rockwool cubes into Hydroton, and cover the top of the cube with Hydroton as well.

If you only have large Rockwool cubes, then rip/cut them into small 1" square segments to germinate seedlings. Place them in a propagation tray & dome or cover them to retain humidity until they sprout. Once they are 2-3 days old, place the small cubes into your Soiless or other Hydroponic medium.





Sunday, January 22, 2012

Don't Burn the House Down!

"My Breaker keeps tripping..."

"My HID Lights won't turn on..."

"I keep hearing loud buzzing or humming noises"

A very common, devastating, and possibly even deadly mistake made by beginner indoor growers is their lack of knowledge regarding electrical components. Most beginners take the time to educate themselves on how to grow and care for plants, however they disregard educating themselves on the technology they are using. Usually it's because the technology seems difficult to learn or out of pure laziness. Not everybody can be an Electrician, and while this is true you should still take the time to learn the basics. Furthermore, you should not take on projects which are beyond your understanding. Seek professional help instead of risking disaster by doing it yourselves.

One of the most important things you need to learn is how to measure amperage to watts properly to avoid breakers from clicking off. Don't be intimidated it's actually alot easier than it sounds. Most houses or apartments have a small breaker box attached to the unit which you have access to should your breakers click into an off position during a short circuit. Almost everybody has at least had to do this once; stumbling in the dark with a flashlight into the basement/garage, or sometimes they are even located outside of the house. Before choosing which room in your home you will grow in, you need to visit your breaker box. Bring a flashlight if it's in an area where there is no light.

A common household Breaker Box - 120v

If you look closely, you will see numbers written directly on the breaker switches. These numbers represent the maximum number of amps each breaker(or room in the house) can handle before turning off for obvious safety reasons. In the picture above the refrigerator, laundry, and heater breaker can handle as much as 20 amps and are on their own separate breaker switches. This is because these appliances consume a wattage higher than 1000 and have a high amperage rating. For example, if you plugged in your refrigerator to your family room(15amp max) then it would cause a short and click the breaker off in the family room. At the same time however if you plugged in multiple appliances to the same outlet that is connected to your refrigerator, then the breaker would switch off as well. This is why it's important not to just choose any breaker with a high amp rating and assume all will go well. It's more beneficial to choose a 15amp breaker with no appliances connected over a 20amp breaker that already has appliances plugged in. Furthermore, if you plan on adding more or more powerful MH/HPS lights later on you don't want to run into this problem then. 

So where should you plug in all your growroom appliances?
I'm gonna let you decide, however I will show you an example. While it looks tempting to run my appliances for my growroom from the master bedroom or kitchen, to me that would be a fire hazard. With a tv, computer, fans or ac/heater, game consoles, lights, alarm clocks, cable box, dvd players, and cell phone chargers there isn't much room for me to add high wattage HID lights. For the kitchen method it would fail the second someone decides to make toast or a margarita. 

If the picture above was my breaker box then here is what I would do:
1. I would choose the unused outside outlet with a 15amp max breaker
2. I would run weather proof cabling from the outside outlet into my growroom(master bedroom)
3. I would plug in no more than 1500W to this connection (even though it can handle 1800W)
4. I would plug in no more than 500W of growing appliances in my master bedroom (so I can keep my personal appliances)
5. I now have 2000W of available, safe, and reliable power.

With this method for example I could use a 1000W HPS for my flowering room, and a 400W MH for my vegetative room with plenty of extra power for fans, heaters, ac's, co2, air movers, air pumps, water pumps, fluorescents, LEDs, and even another 400W HID if I wanted to expand. I could also go another route and use 2X 600W HPS lights for my flowering room, 1X 600W MH light for my vegetative room, and still have extra power available. 

That's cool but what if I want to run multiple 1000W HID lights? 
You would need to make a compromised decision in this case unless you have access to a 30amp or higher breaker outlet. A 20amp breaker outlet will usually handle a max of 2400W, but with other appliances plugged into the outlet it will easily reduce it to lower than 2000W. Therefore you will need to completely isolate the room (with the 20amp outlet) and use it solely for growing appliances. With a 30amp outlet, which can handle 3600W, you would not have this problem.

In Conclusion:
Identify what the maximum amount of amperage is allowed per outlet in your home, and work your gameplan around that. Take into account any appliances which are already plugged into the outlet, and identify their wattage consumption so you can make a calculated decision as to how many watts you have available safely.

  • 15AMP MAX: 1800W
  • 20AMP MAX: 2400W
  • 30AMP MAX: 3600W

***NEVER replace a breaker switch with a higher amp rating without seeking professional help. If you want to change a breaker switch to a higher amp rating you will need to also make changes to your outlet, wiring, and breaker box. Failure to do so will eventually result in a fire!

Wednesday, January 18, 2012

HID VS CFL


This battle has been in debate ever since their existence, just like the 9mm vs the .45acp, or classic Vinyl Turntables vs Digital CD/DVD Turntables. Really it all falls down to what works best for you in your own experience. Here I will share my opinion on the matter so keep in mind this is only my own personal opinion from my own personal experience. This is what works best for me; in terms of space, reliability, electricity consumption, yield ratio, and heat generation.

So let's look at the 3 main things we use a light for; First we need to produce a high amount of lumens to help the plant grow properly. Second, we need to obtain the right color spectrum according to the plant's current stage in it's life process. Third, we need to minimize the amount of heat generated and provide proper air circulation while keeping the light as close to the plant as possible.

===HID vs CFL===
Winner Lumens: HID
Winner Spectrum: HID(flowering) & CFL (vegetative)
Winner Heat: CFL

When it comes to lumens HID wins hands down no contest. Typically, a 400W HID will generate as many lumens as almost 800W of CFLs. However, the HID will produce twice the amount of heat and cannot be placed as close to the plant as the CFL. This means you will need additional air circulation, and in most cases the implementation of a intake and exhaust fan system. Regarding color spectrum, it is my personal opinion that CFLs win in the Vegetative state, and HIDs win in the Flowering stage. CFLs can reach a color spectrum of as high as 6500 kelvins, but can only reach as low as 2700 kelvins for the flowering stage. HIDs, more specifically Metal Halide, only produce bulbs for the vegetative stage as high as 5400 kelvins while most are usually under 5000 kelvins. High Pressure Sodium bulbs are usually 2200 kelvins or less making them perfect for the flowering stage, and making them more efficient than CFLs during flowering.

Where the Spectrums begin:
Blue Spectrum: 4500 kelvins and up
Red Spectrum: 2800 kelvins and lower
Nuetral/UV: 3000-4000 kelvins (Yellow/Green/White)

Q.) What kind of CFLs should I buy for Vegetative Stage?
A.) Most beginners make the common mistake of purchasing multiple low-wattage CFLs in the wrong spectrum for each plant. For example, they would purchase 2-4 bulbs per plant at only 13-18W per CFL, and they would be in the wrong spectrum or "soft white". Scientifically speaking, 13-18W is just not enough power to penetrate plants effectively once they've completed the seedling stage resulting in slow & stunted growth. Using four 13W bulbs will not produce the same amount of lumens as a 52W bulb, however you will still pay for 53W of electricity consumption. Furthermore, it's important to check how many lumens each bulb is producing. Some energy savings bulbs produce less lumens than other bulbs of the same wattage. I've personally seen 23W CFLs which only produce 1200 lumens or less, while other 23W CFLs I've seen produce 1500-2000 lumens. Below are two examples of a proper Vegetative setup using CFLs.

Setup A:
Purchase one high wattage CFL (80-105W) in the 5000k-6500k temperature (spectrum) per plant. Place light as close as possible to plant. Use a basic 2 foot (or 4') fluorescent which can be purchased at Wal-mart/Lowes for under $20 as supplemental lighting. I recommend at least 2 of these florescent per every four plants. Make sure you purchase fluorescent bulbs in the correct spectrum (5000-6500k), however the wattage isn't necessarily relevant as these will serve as supplemental lighting only.

Setup B:
Purchase two lower wattage CFLs (30-40W) in the 6500k temperature per plant. Place both lights as close to the plant as possible. Purchase one more medium wattage (50-65W) CFL in the 5000k temperature as supplemental lighting if you have multiple plants. Place this light in the center of all your plants, and suspend it higher up than your lower wattage CFLs. Use a proper light reflector to avoid wasting light, however you want a reflector that will disperse the light evenly throught your garden as this will be supplemental lighting. **If you have to buy 23W CFLs, make sure they are at least producing 1500 lumens or higher per bulb.

Q.) Where do I buy the Y splitters and plugs for my CFLs?
A.) Home Depot or Lowes are the best place and the cheapest. Ask an employee to guide you, and let him/her know that you are looking for a medium socket converter (to 120V power plug) for light bulbs, and a medium socket 2-way or Y splitter as well. Make sure you are not purchasing a mogul converter (unless you purchased mogul base bulbs) as this wont work for your medium base CFL bulbs.

Y-SplitterHome Depot - Medium Twin Socket Lamp Adapter 660W Max

ConnectorLowes - Medium Light Socket Adapter 660W Max

Q.) Should I buy "cool white" or "halogen white" 3000-4000k bulbs?
A.) Personally I would advise to stay away from these bulbs. This spectrum is absolutely worthless to plants in my own personal experience. Stay away from Flood lights(Halogen) which are usually in this spectrum also.

===Conclusion===

Vegetative Winner: CFL (5000-6500k Full Spectrum/Daylight Blue)
Flowering Winner: HID (HPS 2000-2200k Red)

Metal Halide or High Pressure Sodium?

Technically, either one will do the job, however when both are used correctly they will produce superior results. Let's take a look at some specs for both setups:


Metal Halide:
  • Spectrum: Usually between 4000-5400k (Blue)
  • CRI: 65-90nm (Cool-Full Spectrum)
  • Wattage: Most are between 175-1000W
  • Heat Generated: Medium-High
  • Lumens: 65-115 per/watt (Depending on Bulb)
  • Average Lifespan: 20,000 Hours


High Pressure Sodium:
  • Spectrum: Usually between 2000-2400k (Red)
  • CRI: 20-25nm (Warm Spectrum)
  • Wattage: Most are between 150-1000W
  • Heat Generated: High
  • Lumens: 50-145 per/watt
  • Average Lifespan: 25,000 Hours




Let's take a look at what plants need during their main 2 cycles:

Vegetative:
  • Spectrum: Cool Blue-Full-Daylight Blue (4500-6500k)
  • Wattage to Lumen Penetration: Minimum of 35 lumens per/watt, 100+ Preferred
  • Heat Tolerance: Up to 89F max, however stress will begin at this temperature
  • Lifespan: Average of 6 Weeks minimum, or 756 Hours of 18/6 Spring/Summer Cycle
  • Best Choice of Lighting: Metal Halide @ 50-100W per plant or higher for better results.

Flowering
  • Spectrum: Autumn/Winter Warm Red/Orange (2000-2800)
  • Wattage to Lumen Penetration: Minimum of 50 lumens per/watt, 100+ Preferred
  • Heat Tolerance: Up to 85F max, however stress will begin at this temperature
  • Lifespan: Average of 6 weeks minimum, or 504 Hours of 12/12 Photoperiod 
  • Best Choice of Lighting: High Pressure Sodium @ 100-200W per plant or higher

Kelvins Spectrum


Conclusion:
For best results and highest yields, use MH lights for the Vegetative Cycle, and HPS lights for the Flowering Cycle. This will ensure that the plants are receiving the proper spectrum during the designated cycle given. MH lights will mimic the Spring/Summer sun, and you will leave them on for a minimum of 16-18 hours a day to simulate the longer days when the planet is closer to the sun. HPS lights will mimic the transition as to when the planet is revolving away from the sun bringing forth the end of Summer and the beginning of Autumn. You will simulate these shorter days by only leaving your HPS light on for 10-12 hours a day. 

Running Costs:
Electric companies usually charge by the kilowatt hour(kWh). What this means is for every 1000W of total energy being drawn for an hour, they will charge a specific price. So for example, if you have a 1000W HPS light running at a 12/12 cycle, and your electric company charges $0.23/kWh, then your cost would be $2.76/day or roughly $82.80/mo.

400W MH/HPS @ $0.23/kWh:
20/4: $55.20/mo.
18/6: $49.80/mo.
12/12: $23.00/mo.
600W MH/HPS @ $0.23/kWh:
20/4: $82.80/mo.
18/6: $74.40/mo.
12/12: $49.80/mo.

Pythium, Root Rot, and Damping Off Hydroponics & Soiless


Fighting off Pythium, Root-Rot, and/or "Damping Off" in Hydroponic or Soiless Mediums 


Applies to all tropical & sub-tropical flowering (bulb) plants (e.g. tomatoes, cucumbers etc.)


**Not recommended for root based (onions/garlic etc.) plants or organic mediums


Rotted Seedling Before Sprouting

Left: Healthy Seedling - Right: Seedlings infected by Pythium 

Damping Off or Root Rot can happen anytime during the plant's life cycle, and yes even during germination. It is the number one cause for dead plants, and is as common of a disease to plants as distemper and parvo are to K-9s. It will manifest under any wet conditions, and will especially thrive during dark times when you turn the lights off. Furthermore, it only takes a single spore to infect your whole garden, so to add insult to injury, it can completely devastate your whole garden within less than 24 hours if left untreated. Mother Nature deals with this fungus naturally by providing H202 naturally during the spring rains, and by drying the topsoil with heavy winds. Plant genetics also play a big role in determining how much mold/fungus a plant can tolerate before succumbing to the disease. 

========================================================================

Common culprits of "Damping Off":
1. Overwatering
2. Too much humidity
3. No airflow and ventilation
4. Cross-contamination and/or unclean growrooms
5. High reservoir temperatures

First off, you need to make sure your environment is not the problem:
Q1: Is there a high level of humidity 70%+ in your grow room?
Q2: Is there a fan(s) or proper air circulation in your grow room?
Q3: Are your reservoir temperatures 75 degrees F or higher?
Q4: Is your grow room littered with trash/dust/soil/medium?
Q5: Are you using any medium/pots/trays from a previously infected plant?

A1: Humidity should not be higher than 70% for seedlings. Use a de-humidifier if needed.
A2: Air circulation over the top of your medium will dry the top layer faster; preventing the disease.
A3: To simply reduce your reservoir temps freeze a few plastic water bottles and place into reservoir.
A4: Keeping your grow room clean will prevent disease and pests from manifesting.
A5: Cross contamination will happen so throw away old medium, and dissenfect trays/pots with bleach/water.

========================================================================

Germination
*Add 1 teaspoon of h202(3%) to 16.9oz of untreated tap water to germinate.
*Spray inside of humidity dome/bag with 10/90 bleach/water.
*Continue using water & h202 mix to re-hydrate towel/medium.
*If germinating in Rockwool do not allow medium to sit directly in water.
*Humidity should not be higher than 85% for optimal settings.

Seedling 
*Add 3 teaspoons of h202(3%) to 16.9oz of untreated tap water to hydrate
*Apply fungicide once a week but dilute normal dossage with h202/tap water mix
*Apply a few drops of cloning gel at the base of the stem once a week. If using powder dillute in water.
*Humidity should not be higher than 70% and should be kept at 65% for optimal settings.
*If sprouted in Rockwool make sure you allow medium to fully dry out between waterings.

Vegetative
*Add 5 tablespoons of h202(3%) to 1 gallon of untreated tap water to hydrate.
*Apply a few drops of cloning gel at the base of the stem twice a week. If using powder dillute in water.
*Flush your reservoir and pipes with 50/50 bleach/water at least once every 10 days.
*Allow reservoir to completely dry and stay dry for 4-8 hours before filling back up.
*Avoid using shared reservoir hydroponic systems to prevent the disease from spreading.
*If using DWC hydroponics then provide as much air bubbles as possible. Use quality high power air pumps.
*Do not allow Rockwool to sit directly onto water level. Use Hydroton/Clay to seperate water from Rockwool.
*If using Flood&Drain allow medium to completely dry out for 6-8 hours before re-hydrating.
*Place Hydroton/Clay medium into a strainer, spray with bleach, and rinse thoroughly before using.
*Allow Rockwool to sit overnight in water before using to fully rinse out unwanted material.
*If using soiless mix water heavily and allow pot to completely drain/dry out for at least 48/72 hours.
*If using soiless mix use Hydroton to cover the top layer of soil to 1.5-2". This keeps the top layer dry.
*If using soiless mix use plenty of Perlite and/or Hydroton to allow easy water drainage and aeration.
*Humidity should not be higher than 70% and should be kept at 60% for optimal settings.
*Temperature should be kept between 70-85F(21-29C) to maintain a healthy plant. Healthy plants fight off disease.

Flowering
*Add 4 tablespoons of h202(8%) to 1 gallon of untreated tap water to hydrate.
*Add a few drops of fungicide to the same 1 gallon of tap water.
*Add a few drops of cloning gel or powder to the same 1 gallon of tap water.
*Continue to flush your reservoir and pipes with 50/50 bleach/water at least once every 10 days.
*Continue to allow reservoir to completely dry and stay dry for 4-8 hours before filling back up.
*If a plant becomes infected instantly quarantine and treat it in a seperate room. Return once fully recovered.
*Increase ventilation during the flowering stage and keep the room clean and sterile.
*Humidity should be kept below 60% at all times. For optimal settings keep humidity between 40%-50%.
*Temperature should be kept between 70-85F(21-29C), and no lower than 62F(16C) during the night cycle.


Supplies
You should always keep these supplies handy to prevent and treat any type of root rot.
*H202(3%) and H202(8%) - Regular over the counter Hydrogen Peroxide
*Root hormone/cloning gel or powder
*Fungicide
*Bleach
*Sterile tools
*Standard 16.9oz water bottles
*Standard 1 gallon water jugs
*Recommended for Soiless Mediums: Moisture Sensor for accurate watering periods.
*Thermometer & Relative Humidity sensor which can record highs/lows over 24-48 hour periods is needed at all times for quick and accurate diagnostic.