Aside from proper lighting and temperature, one of the most critical areas that will require your regular (daily) monitoring is maintaining your nutrient solution and reservoir. There is nothing you can do to force your plants to grow. You can only provide the best conditions. After that, relax and let your plants do the rest. Download the free GYOstuff Hydroponic Garden Daily Monitoring Log to help you track and perfect your hydroponic garden.

Beginning Water Quality
Good hydro farming starts with water quality. Check your tap water with a TDS (total dissolved solids) meter. If it’s over 200 PPM, you should use a reverse osmosis filter, or bottled spring water.

If your hydro setup does not include water purification or bottled spring water, it is a good idea to let tap water sit out overnight in an uncovered container for two reasons. First, this lets the water dechlorinate - Chlorine dissolved in the water escapes into the air. However, if you have chloramine, a newer additive used in place of chlorine in some water systems, it will not leave the water when exposed to air. You have to check with your water supply company to find out which they use. Second, allowing the water to sit out overnight also lets the water become room temperature. Adding cold water will shock the roots, causing root damage as well as above ground damage. For more information about measuring PPM and water quality, check out our page about What PPM Scale To Use.
Nutrient Solution pH
If you want to maximize your yield and plant health, you must monitor pH (potential hydrogen). The nutrients are only good to the plants if the pH is right. pH is the measurement of the acidity or alkalinity of the soil or growing medium. A pH of 7 is considered neutral. A pH below 7 is acid and above 7 is alkaline. Most plants want a pH of between 5 and 7 (slightly acid). When selecting different plants, you should take the pH into consideration so that all plants in each system have similar pH and PPM requirements. pH adjustments can be made with either liquid or powder.

The maximum nutrients are available to the plants in a pH range of 5.5 to 6.5 (hydro) and 6.5 - 7.3 (soil). Tap water is usually between 7 to 8 pH. In hydroponics, the nutrients are often kept at about 5.5 because the plants absorb the nutrients slightly more quickly at this pH.

Also, the natural tendency is for the pH to creep up over time. Therefore, you must adjust the pH down to the low end of the range when you make an adjustment.

Rule of thumb for adjusting pH - go slow! Correct the pH a little bit, then measure until you get a feel for which way things are going. If you go too far with pH adjustments, you can really upset your system.

Always use rubber gloves when handling concentrated pH adjusting materials like phosphoric, sulfuric or nitric acid, or potassium or sodium hydroxide. We do not recommend using sodium hydroxide or vinegar for adjusting the pH.

Nutrient Solution Strength
Successful growers use a total dissolved solids (TDS) meter or an electrical conductivity (EC) meter to tell how strong or how weak the nutrient solution is. The ideal strength of your nutrient solution depends on what type of plants you are growing, and also what stage of the plant life cycle they are in. For the first week of growth, mix your hydroponic nutrient solution to 50% of the normal recommended strength.

Parts per million (PPM) is a way of measuring how much nutrient is in the solution. PPM is measured electronically on meters. Target PPM ranges:

  • Seedlings, Early Sprouts 100 to 250
  • Early Vegetation 300 to 400
  • Full Vegetation 450 to 700
  • Early Blooming 750 to 950
  • Full Mature Blooms 1000 to 1600
If PPM is going up, the plants are drinking more than they're eating. If PPM is going down, the plants are eating more than drinking and your next mix could probably be a little stronger. If it's going up you’ll probably see the telltale signs - maybe tiny burnt leaf tips. If the nutrient strength is a little weak, add a little fertilizer. If the nutrient strength is a little high, add plain water.

When measuring PPM, you should know that there are two different scales that are both widely used - the "500" scale (fresh water) and the "700" scale (salt water). In order to be sure you're using the correct one, you need to know what scale the nutrient manufacturer bases their formulas upon. Sound complicated? Don't worry. We did the research for you. Click here to find out what PPM scale your nutrient manufacturer uses.

Maintaining your Nutrient Solution
In a small (5-10 gallon) reservoir, you should check the strength (TDS or EC) and the pH of your solution once or twice a day. With a larger reservoir, the changes in the nutrient solution take more time. We recommend you check your nutrient solution once a day, no matter what size reservoir you have. Successful growers usually use a larger reservoir. Download the free GYOstuff Hydroponic Garden Daily Monitoring Log to help you track and perfect your hydroponic garden.

The nutrient solution temperature should be between 65oF and 68oF.

Change it Every Two Weeks – MAX!
After two weeks of using the same nutrient solution, it is time for a nutrient change. The plants may have been using some nutrients more than others which can cause a nutrient imbalance. Keep an extra nutrient reservoir full of plain water waiting for your next nutrient solution change. This ensures you will have dechlorinated, room temperature water that will not damage your plant's roots.

It is a good idea to run a tank full of plain water (or 1/4 strength nutrient solution) for a day in between nutrient changes, to flush out any nutrient buildup. Some experienced gardeners do this every four weeks, or every other nutrient change.

A Fair Warning
When plants do not have to grow roots into soil to "mine" for food, they use that extra energy to grow rapidly above ground. These rapid growth rates are the biggest attraction to hydroponics gardening.

However, if conditions are not kept right this can also be your biggest problem. The only way the plant gets to stay lazy is for you to keep giving it exactly what it needs every day. If you don't, the plant has no other backup plan...there will be damage. Since growth rates are fast, the damage will happen quickly.

Perfecting Your Nutrient Solution
Once you have a simple feeding plan that is working well, you can try to maximize your results. The best advice here is to make small changes, one at a time, and let each change show its effects before making another change. Sometimes this will mean waiting two weeks, other times it may mean waiting a whole crop cycle for the results.

Experience has shown that a simple plan with high quality results is what your goal should be. Many times, experimenting only leads to bad results. To make matters worse, if you changed two or more things, you’ll have no idea what is causing the problem now. Don't forget to always document your grow if you want to review and improve upon your methods.

The Final Flush
It’s best to do a final flush just before harvest. Flushing the crop helps remove any fertilizers in the plant tissue. Flushing will improve the flavor and aroma of the produce in your garden. You can flush using plain water for 7-10 days or you can accelerate the flushing process by using a flushing solution.

By reducing the amount of time needed to flush (if you're using a flushing solution), you're increasing the amount of time your plants can be receiving their full nutrient program. This will lead to a bigger harvest. So, what's the best way to flush? Using a flushing solution.

Want to learn more? Check out the other topics in the GYOstuff Learning Center.
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