Hydroponics attachment and hydroponics kit

A hydroponics attachment comprising:

• a cap member which is, via a threaded portion preformed on a mouth of a drink bottle for cap attachment, detachably screwed on the mouth of the drink bottle, and has an opening formed on an upper surface thereof;
• a case body shaped like a cylinder with a bottom, which is fitted in the opening of said cap member;
• and
• a water-holding element placed in an interior of said case body, for absorbing water stored in the drink bottle, so that hydroponics can be carried out with use of the water absorbed by said water-holding element,
• said water-holding element being designed in single-piece structure with use of a plurality of filaments,
• said case body having at its lower end an insertion hole in opening form for guiding a root of a plant growing downward through said water-holding element to go down below the case body,
• said insertion hole having an opening dimension which is smaller than an outer dimension of said water-holding element.