The job of a spawning brush is to catch eggs, and these spawning brushes are 96" / 240cm, because Koi are large fish which scatter thousands of adhesive eggs.

Leave koi, goldfish or other pondfish and they'll just spawn all over the pond, usually in the warm shallows, in some aquatic plants or marginal plant roots, but if you want a good chance of raising what could be some valuable progeny then you use these brushes.