The most common fish fertilizer (emulsified fish viscera/ FE) has NPK %s of 5:1:1, which means it's very high in N and low in K. Fish emulsion is not a good stand alone choice for long term care for the simple reason it contains only N, P, and K. Plants need a full compliment of nutrients normally assimilated through the root pathway if they are to grow normally and keep their systems and processes orderly.
Since FE cannot be considered to be an effective single source of nutrition, and use of other fertilizer products to 'fill in the nutritional gaps" is essential for best results, it makes much more sense to simply purchase a single product that already has everything it needs to be called a single source of nutrition.
Foliage-Pro 9-3-6 is a superb, one-step product for almost everything you might choose to grow in a container. If you ask, I'll provide a list of its many attributes.
Al
