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Hydro Nutrients Faq

Guidelines for Hydroponics System Nutrients:

There are a great deal of different Hydroponics systems available, both active and passive, but they all work on the same principle.

Chemical salts are dissolved in water, to provide the nutrients that the plants need to grow. These nutrients are then delivered to the root system of the plants in a variety of ways – either by simply watering the plants with the nutrient solution by hand (called Passive Hydroponics) or by automatic watering of the plants via a pump from a nutrient tank (Active Hydroponics).

There are lots of quirks with each system, but a few factors remain constant.


The PH of your nutrient solution should be within the range 5.5 – 6.5 each time the plants are fed. It is better to be closer to 5.5 – 6.0, as above this range, the plant cannot take up many of the micronutrients, and so deficiencies may occur.

In order to achieve this, the solution often has to be ph adjusted down (especially in hard water areas, where the ph of the tap water can be in excess of 8).

This is usually achieved by adding Ph Down to the solution – usually a chemical called Phosphoric Acid.

This is not ideal however. This almost always causes a build up of phosphorus in the plant tissues over time, especially as most bloom nutrients contain a great deal of phosphorus anyway, and flower boosters such as Ionic Boost and PK13/14 contain even more.

Excess phosphorus in the plants makes the smoke much harsher, and on a more serious note, can increase the risks of cancer and other illnesses.

Where possible, it is recommended to use another method of controlling the PH. Nitric acid is available from some growshops – this gives you an excess of Nitrogen in the tissues, which can make the plants stretch a little, and can also make the smoke harsh (especially before curing), but is not as bad for you as excess phosphorus.

Nitric acid is also highly corrosive, so its very important to wear rubber gloves and eye protection when using it

Citric Acid (lemon juice or powdered citric acid) is a much better way of correcting ph – just be aware that you may need to use a lot of it, especially if you are in a hard water area.

PH problems are one of the most common causes of plant illness – check it using either a liquid indicator kit or a digital meter before each feeding, or once a day in an active system. If you need to balance the ph make sure that your pumps are turned off while you do it, and that you give it at least half an hour after balancing before giving it to the plants, to make sure that the acid is evenly disbursed in the solution.


This is the concentration of your nutrient solution, and is measured with a digital meter of truncheon. This is a vital piece of equipment when growing hydroponically

The final CF of your nutrients should be in the range of 1.5 – 1.8, after PH balancing and all additives have been put into the tank.

Contrary to what many people think, higher nutrient levels do not make the plants grow faster or larger – often its quite the opposite, and very high CF levels can kill the plant stone cold dead.

The instructions on many hydroponic nutrients give maximum levels – the amounts stated on Canna nutrients will give you a CF of 2.2 – 2.5, which is far too high.

Also, by over feeding the plants, all of the excess chemical salts are retained in the buds and leaves – which means that you end up smoking them – these are really not good for you, and over time can cause all sorts of health problems (and can also affect the taste of your weed badly if you need any more convincing).

As your plant takes up water, there is less water for the nutrients to be dissolved in, and so the CF goes up (unless they are properly balanced, in which case they should remain constant) – it is a good idea to top up your reservoir with ph adjusted tap water to prevent this happening – that should stop the CF levels going through the roof.

If your CF is dropping, then simply let a bit more water be taken up, and top up to a lower level to keep the CF at the optimum level.

You should change your nutrients either once a week, or at maximum, once a fortnight, as many of the required chemical salts will have been used by the plant in this period. Regular changes keep things balanced at the optimum levels.

In between nutrient changes, you should run an active system for 24 hours on ph adjusted water only. This is called a wash through, and prevents chemical salts from crystallising on the roots (preventing the plant from taking more nutrients up). After the washthrough, you should then drain the tank and refill it with water, to make the fresh batch of nutrients up.

In between nutrient changes it is EXTREMELY IMPORTANT not to dispose of your nutrients down the drain, or down the toilet. All of those chemicals end up in the water supply that we all drink, and messes up the environment. Pour them into your garden, onto your houseplants or whatever. Don’t be a tosser and fuck up the environment with your waste nutrients. If you do, you are no better than a chemical company that dumps its waste into a river or the sea.

Lastly – nutrient temperature. In an active system, it’s a good idea to invest in an aquarium heater to keep the temperatures of the nutrients at about 22 degrees C.

Not only does this help the plant take up the nutrients better, but it means that your CF and PH will be more stable, as water holds different amounts of dissolved solids at different temperatures. Keeping your nutrient temperature at about that level will give you much more consistent results.

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