While there are numerous advantages to using seaweed fertilizer, there are also a few potential disadvantages to consider. One drawback is that the high salt content found in some types of seaweed fertilizers may harm certain sensitive plant species or cause damage if applied excessively. Additionally, the strong odor associated with many seaweed products might be unpleasant for some individuals during application. Another challenge with commercial seaweed fertilizers is that they can be costly compared to other types of organic or synthetic fertilizers available in the market. Lastly, sourcing large quantities of fresh or dry seaweed may be difficult depending on your location if you prefer making homemade fertilizer preparations from scratch.