Sometimes the amount of fertilizer applied is insufficient to stimulate phytoplankton response. If storage is required place chemical fertilizers in a dry, well protected location. Excess humidity can damage the fertilizer. Bags of fertilizer can be stored on simple wooden or bamboo platforms elevated above ground. Buy the fertilizer you need.
Some companies sell a variety of fertilizers.
Inquire from extensionists and other farmers which fertilizers they recommend for fish ponds. Fertilizer grades are usually marked on the bag or box containing the fertilizer. Some companies guarantee this analysis. Buy chemical fertilizer from a reputable dealer. It is difficult to determine when chemical fertilizer is no longer usable.