The standing crop and the production rate of the algae attached on the experimental stones were studied for one month from September to October, 1973 in Cheonji stream, Cheju Do. The results are summarized as follows: 1. The standing crop of the algae was estimated at 29.47 gr/㎡ in wet weight for one month. The production value was almost equal to that of the result in the Gangjung stream, Cheju Do, but this value was much smaller than that of the other streams. 2. Comparing the food intake value of Plecoglossus altivelis to the standing stock, the density seems to be over-populated almost 3 times of the equilibrium population size. 3. From the fact that the average production value per day was 0.31gr/㎡, the algae should grow for approximately 26 days to reach the level of the average standing crop under the natural condition. 4. The production peak reached during the first 5th to 7th day after staying stones, at which time the production value was 0.75 gr/㎡ per day. Within the first 7 days, about 49% of the average standing crop was obtained, at that time, the corresponding coefficient was 2.17. 5. From the fact that the turnover rate of the algae decreased after 10 days, it is expected that the continuing consumption can accelerate the production rate.