Cheap Kratky Method | How to Start an Indoor Hydroponic Garden

Indoor hydroponics doesn’t require expensive countertop gadgets: a Kratky-style setup lets gardeners grow vegetables indoors using simple containers, net cups, and a controlled air gap so roots can breathe. The method works by suspending a plant so its roots sit in water while a gap above the waterline provides oxygen—removing the need for pumps or electronics and reducing mess compared with soil-based indoor growing.

The build centers on a “Kratky jar” arrangement. A mason jar is the most common container, and amber jars are recommended because their brown tint blocks more than 99% of light, helping prevent algae. Clear jars can work too, but light exposure increases algae risk. For budget alternatives, the video describes repurposing household items: a Dollar Tree vase can fit a 3-inch net cup, and an ice cream bucket can be converted into a light-blocked reservoir by covering it with black duct tape. The key is matching the container size to the plant and ensuring the top has a hole (or a compatible opening) sized for the net cup.

Plants are held above the water using net cups (often 3-inch), with clay pebbles underneath to stabilize the plant and keep light from penetrating downward. The roots either start in the Kratky system or are moved in from an Aerogarden. When transferring an already-rooted plant, the video notes that some net cups are too thick to thread roots through, so thinner cups (or cups with cuttable bottoms) can be used. For smaller plants, feeding roots through the cup opening is easier; for larger, thicker root systems, it may be difficult to remove or reposition the plant later.

Starting from seed requires a rooting medium such as rockwool (or Aerogarden sponges). Seeds go into the sponge, which sits inside the net cup. A layer of rocks can be used to raise and center the sponge so it stays stable. During germination, the setup can be left exposed to light, but once growth begins, the seed area should be covered to block algae—thin net cups that include covers are presented as a practical solution.

Water level management is the other critical detail. In smaller 32-ounce jars, the video uses a marked fill line (400 milliliters) and refills no higher than that. The water gradually drops as the plant grows, and the gardener aims to maintain a small air pocket for oxygen. For longer-term growing without frequent refills, larger reservoirs—one gallon, two gallon, or five gallon buckets—are suggested, especially because outdoor heat increases evaporation.

Finally, indoor success depends on light. Seedlings should be placed under a grow light; the video mentions a “Root Farm grow light” and describes positioning plants near existing Aerogarden units. With inexpensive materials—jars, clay pebbles, a grow light, and basic components—the method is presented as a low-cost way to grow peppers, tomatoes, herbs, and lettuce indoors without soil and without electronics.