Anyone looking for an organic fertilizer has heard of fish fertilizer for plants. Further research will reveal three very different types: hydrolyzed fish, fish meal and fish emulsion. If the label does not clearly state which it is, check the nitrogen(N) levels; anything over 4 must be an emulsion (fish naturally contain about 2.3%N).
The difference between the two is not that of good vs. evil, but rather the difference between a product that works and one that works once, then continues to work long after application. Ocean fish contains the full range of nutrients, vitamins, amino acids, enzymes, and growth hormones. Seawater is the world's single source of nature's balanced vital elements. The 90+ elements on the periodic table are the same micro-nutrients plants need; hydrolyzed fish fertilizer can deliver these nutrients to plants. Garden soil can become balanced, hosting a living micro-community, and therefore grow plants of amazing beauty.
Hydrolyzed fish fertilizer for plants has the consistency of chocolate milk, and though it smells, it is more of a fish and low tide smell; it doesn't smell good, but there is something fecund in it that makes it not smell bad. This thick liquid is actually ground and micro-screened fish carcasses; the fillets are for human consumption, everything else goes into the grinder. Only North Atlantic fish that are caught at least 3 miles offshore are used, allowing the fertilizer to meet organic standards. Because the fish are cold processed, none of the essential nutrients are lost.
Fish emulsion is a by-product left over when processing "trash fish" (fish you won't eat). Fish meal (the meat protein) is removed, then the oils are removed. Whatever is left over is boiled down to a 50% solution and sold as fertilizer. This process has two major problems: 1) chlorine is used in processing and 2) heat destroys all the essential nutrients. Fish emulsion smells like old rotten fish, and has a syrup-like consistency which tends to leave residue in sprayers.
Fish meal is a fish fertilizer created from dried fish waste, where the rancid oil is removed and preservatives are added. Since this is a slow-release fertilizer with a high content of primary and secondary macro nutrients, it is beneficial for leafy plants. Fish meal is also a good source for micro nutrients and provides food for good bacteria in soil, resulting in larger, stronger plants.