Seaweed seeds are really needed to meet the needs of seeds for community cultivation activities, both in terms of quantity and quality in a sustainable manner. Tissue culture seeds are quality seeds produced in the laboratory, and one of the factors that determines the continuity of production is the ability of the seeds to adapt to the acclimatization phase outside the laboratory. Based on the results of previous trials, the culture of young seaweed seedlings resulting from tissue culture (plantlets) without fertilizer in the laboratory gave the highest LPH, namely 7.05 ± 0.25%, but was weak when acclimatized in the greenhouse, while culture without fertilizer in the laboratory was more efficient than using fertilizer. Therefore, this activity was carried out to find a method for pre-acclimatization treatment of cultured plantlets without fertilizer that can increase the growth and survival of plantlets in the acclimatization phase to ensure the continuity of quality seeds for cultivation. This activity uses kotoni plantlets (K. alvarezii ) cultured without fertilizer in the laboratory, where the plantlets are divided into two for treatment, namely: A1. Culture was continued without fertilizer and A2. The culture was given additional fertilizer, which was carried out for 2 weeks in the laboratory. After that, the culture was continued in 2 aquarium units in the greenhouse for acclimatization, where both cultures were given the same treatment, namely the circulation system. The results obtained showed that the LPH of plantlets that were given additional fertilizer during the treatment period (2 weeks) was higher, namely 4.64% and during acclimatization in the greenhouse for 6 weeks, had an LPH of 4.10% with an SR of 100%. Meanwhile, the LPH of seedlings without the addition of fertilizer during the treatment period was 1.94%, and experienced bleaching/complete death in the 2nd week of acclimatization in the greenhouse. Thus, the treatment method of adding fertilizer to plantlet culture without fertilizer for 2 weeks in the laboratory before acclimatization in the greenhouse, has been proven to increase the growth and SR of seaweed seedlings in the acclimatization phase, thereby supporting the efficiency and continuity of production of quality kotoni seaweed seedlings.