Kratky pH, Nutrients and Safety

The practical side

Kratky pH, nutrients and safety are the three things worth getting right from the start.

This page covers the parts of the method that need the most care: nutrients, pH, water temperature and safe handling.

Nutrients

Use a nutrient made for hydroponics. Follow the label for strength, and mix it in clean water.

pH

Check the water pH with a meter or test kit. Adjust it with the product recommended on the nutrient label.

Safety

Keep nutrients and pH products out of reach of children and pets. Wash your hands after handling them. Take care with sharp tools.

Sun and heat

Keep the reservoir out of direct sun to stop algae and heat build-up.

Choosing a hydroponic nutrient

Pick a nutrient labeled for hydroponics, not a soil fertilizer. Some are one part; others come in two or three parts that are added to the water separately, never mixed directly with each other. Read the whole label, including the rates for seedlings and for mature plants, and measure carefully. When in doubt, use a little less, not more.

Checking and adjusting pH

pH affects whether plants can take up the nutrients in the water. Test strips, drops or a digital meter all work; meters need calibrating from time to time. Leafy greens generally prefer slightly acidic water. Use the range and the pH up or pH down products recommended by your nutrient's maker. pH adjusters are concentrated acids or bases, so wear gloves and eye protection and add them a little at a time.

Water and heat

Warm water holds less oxygen, and roots in warm, still water are more prone to rot. Keep containers out of hot afternoon sun, away from heaters, and in a room that is comfortable for people. Dark or covered containers also prevent algae, which competes with the plant and can clog roots.

Safe handling

• Label nutrient and pH bottles clearly and store them out of reach of children and pets
• Never store mixed solution in drink bottles or cups
• Wash your hands after handling nutrients, pH products or the solution
• Drill lid holes with the right bit; it is safer than cutting plastic with a knife
• Place glass jars where they cannot be knocked off
• Keep grow lights, cords and plugs away from water

Cleaning up between plantings

When a plant is finished, empty the container, wash it and the lid in hot soapy water, and rinse well. Clay pellets can be rinsed and reused. Rockwool cubes are usually discarded. Many growers pour leftover solution on outdoor plants rather than down the drain; check your local guidance.

If something goes wrong

Most problems come from four things: not enough light, water that is too warm, light reaching the water, or nutrient strength or pH that is off. Check them in that order. Brown, slimy, bad-smelling roots usually point to warm water or too small an air gap; a fresh start in a clean container is often the quickest fix. Yellowing leaves often mean the plant needs more light or more nutrients. Note what you tried, so you can see what worked.

Time and cost

Setup takes a few minutes per container, and daily care is a quick look. Most of the cost is the first bottle of nutrient and the pH kit, which last for many plantings. Jars, net pots and clay pellets can be reused for years.

Food safety

Kratky plants are grown in nutrient solution, not soil, but the leaves still need washing before you eat them. Do not eat any part of a plant that has touched pH products directly, and discard leaves that look slimy or moldy. Use only pest products labeled for edible plants.

Electrical safety with grow lights

A Kratky container needs no power, but a grow light does. Mount it above the plant, not where it could fall into the water, and keep cords and plugs well away from spills. A timer saves you switching it on and off and keeps the light schedule steady.

Questions beginners often ask

Why do the roots look different at the top and bottom? Why is the water level dropping so fast? Why are the leaves turning yellow? The FAQ answers these and more, and the six steps in Make a Kratky Garden cover each stage in detail.

Reading a nutrient label

A nutrient label lists the amount to add per volume of water, often with separate rates for seedlings, leafy growth and flowering or fruiting plants. Use the leafy growth rate for greens and herbs, and stick to it.

Keep a simple log

Note the date, the nutrient amount and the pH each time you mix or top up. If a problem appears, the log shows what changed.