In general, if you’re running a hydroponic system using coco coir (a very common setup), the pH should be sitting between 5.5 – 6.5. When the plants are in the growth phase, the optimum pH is 5.8 – 6.2. If you run into a pH fluctuation, your plants may be unable to absorb certain nutrients that are considered “slow moving”. Get yourself some pH measuring equipment such as pH pens to keep tabs on this.

When your plants are flowering it becomes very important to maintain the proper nutrient factor. Also, when this occurs, keep the pH between 6.0 – 6.4. Neglecting to do this will keep the plants from processing the necessary nutrients and will serve to lower the quality of your result and yields. 

The basic time frame rule is: 18 hrs. on and 6 hrs. off (darkness). Once you see that your plants are beginning to flower, this should be changed to: 12 hrs. on and 12 hrs. off. But you need to keep in mind that once the plants begin to flower, you can’t allow the dark period to have any interruptions. If, somehow, some light leaks in to your crop during its dark period, it will reset the plants back to their vegetation state. It can even cause plant mutation – and you certainly don’t want that!

It depends. Keep the nutrient solution between 18.5 C and 21.5 C degrees. If your crop is in a cold room, you’ll need a heater for the water. Take note that the plants will cease growing and enter shock if the nutrient solution temperature dips below 15 C degrees. If the solution temperature is above 23.5 C degrees, you can find yourself growing harmful bacteria.

Needless to say, there can be quite a few reasons for this to happen. The obvious things, of course are insufficient water, wrong temperature and lack of nutrients. Some of the less obvious reasons can come from root diseases, such as pythium. However, the biggest cause usually stems from incorrect temperature maintenance. It’s also a good idea to use nutrient conditioners in order to help prevent growing harmful pathogens.

Actually, this can be caused by feeding them way too much food. What happens is that nutrients will accumulate in the reservoir tank. This causes the buildup of salt. In any case, it’s always a good idea to flush out your water tank on a regular basis. 

There are also various nutrient issues that can cause the burning of you leaf tips. Most of these problems can be avoided by using EC and pH meters.

As with burning plant tips, this can be caused by several problems. These include; too much salt in the water, incorrect pH, not enough nutrients and oxygen levels that are too low (due to over watering or too little aeration). This is yet another issue that can be avoided through the use of a pH pen and EC meter.

Plants will stretch when either the humidity is too high or there is not enough light. This can be avoided by keeping an eye on the plant’s airflow and overall environment. This can also occur when the light source is placed too far away from the plants or if there are too many plants competing in the same small space.

This is a big issue. Overall basic guidelines are:

• Growth (vegetative) phase – 40-70%
  
• Flowering (blooming) phase – 40-55%
  
• Drying the plants – 40-55%
  
• Storing (curing) – 50 – 63%
  

Too much humidity can lead to mold infestation. Grey mold will quickly spread all throughout the crop.

You can deal with this issue by mounting a hygrometer on the inside wall of the hydroponics growing environment. For all practical purposes, if the humidity sits just above 50%, then you’re fine. You should also keep the nutrient reservoir from adding to the humidity factor by keeping it covered.

For controlling the humidity (and temperature), extractor and intake fans can be used. Remember to keep the growing room relatively dry, as to prevent mould from growing.

This is another major issue. The growing room temperature should be kept between 24.5 – 29 C degrees, when the plants are in their vegetative state.

For the flowering state – between 22.5 C and 26 C degrees.

And for the drying state – 20 – 21.5 C degrees.

Maintaining these temperatures is not all that difficult. This is especially true when you have the lights turned on. If you live in a warm climate, you can use extractor and inlet fans to cool things down a bit. A room heater can be used when the room is too cold.

In addition, your temperature maintenance equipment can be automated with the use of a thermostat device. This can be invaluable in order to prevent drastic temperature fluctuations, which can damage the plants.

The size that you need for your reservoir will depend on your system’s type and the feeding requirements of your plants. This will usually equate to a minimum growing area of 45 liters per/m2. You’ll want to adhere to this size, since using less will entail frequent adjusting.

You also have the option of a deep water culture system (DWC). This allows for a larger volume of nutrients and water. You will have the ability to have this system plumbed to a reservoir that is located externally. When your solution gets low, this system can then automatically add additional solution.

It depends on the type of plants. This is because some plants take a long time in order to develop its new leaf sets. So you will want to refrain from removing large leaves that have taken the plants a long while to grow. However, there are many times in which pruning may be necessary in order for the lower leaves and shorter plants to get sufficient light.