Liquid fish fertilizers come in different forms and qualities. Generally they are either emulsions or hydrolysates.
A fish hydrolysate fertilizer (which is what this product is - it's not a fish emulsion) means that the fish are enzymatically cold pressed, keeping the oils, amino acids, vitamins, hormones, and enzymes in the product. The result is a nutrient-rich concentrate that has many trace minerals and other benefits.
(By comparison, in fish emulsion fertilizer products the important oils etc have been been either separated for use in different products or killed in the high temperature manufacturing process. The result is generally a lower quality product with a lower nutrient content than a hydrolysate.)
At NPK values of 2-3-0, this natural slow-food, broad spectrum fertilizer nourishes the soil ecology and, once diluted, will not burn or pollute.
Organic fish fertilizer is often applied with effective microorganisms, mycorrhizal fungi, compost tea other liquid organic fertilizers. Many people swear by this as a foliar feed. If mixed with EM and water and perhaps humic acids, and left to sit for a few hours before application (but not too long), the slight odour will be drastically reduced.
I have done a fair bit of research on the sustainability of this particular product, called "Pacific Natural", and from what I can gather, it is okay. While it is my belief that we should be careful not to overfish our seas as many species are threatened or already extinct, the Pacific Dog Shark is apparently fished sustainably here in BC below the total allowable catch.
The fishery that supplies fertilizer fish for this product is in the process of undergoing third party assessment by the Marine Stewardship Council, at a cost of more than $100,000. Also, the product uses fresh fish that are a byproduct of goods made for human consumption, therefore diverting them from the landfill.
How much do you need? The recommended application rate for soil is 10 gallons/acre (900 mL/1,000 sq ft), and for foliar sprays 5 gallons/acre (450 mL/1,000 sq ft). The product is a concentrate, and should be diluted at least 1:10 with water for soil application and 1:50 for plant/foliar treatment.
This means one liter of Pacific Natural fish fertilizer, diluted in 10 liters of water, covers 1,100 square feet of soil. Or, 100mL of fish, diluted in one liter of water, is good for 110 sq ft.
To spray plants, dilute one liter of fish in 50 liters of water to cover 2,200 square feet of area. Or, four teaspoons (20mL) of fish, diluted in one liter of water, to cover 44 sq ft. Don't worry too much about the square footage. Just dilute 1:50 and spray till leaves are dripping wet.
Turf: Castle Pines golf course applies 180mL/1,000 sq ft weekly and as high as 540mL/1,000 sq ft during heavy use such as tournament play.
The fish hydrolysate is mixed with water in a watering can, sprayer, or irrigation system. It is best applied early in the morning, while evening would be the second choice. Preferably, liquid fish fertilizer is applied in smaller, regular does, monthly or even weekly. The hydrolysate will separate during storage (oils floating at the top), so shake well before mixing.
In order to receive maximum benefit from the fish, it should be applied separately from sea minerals.
How long does it keep? Fish fertilizer is good almost indefinitely if stored with the cap on tight, out of direct sunlight, and at cool room temperature. It will go smellier over time, so you might want to use it up within about a year. Mix and use only what you want to apply the same day. Diluted mixed product does not keep long.
Here is some more information on application rates. If you have time, you may want to go through them all, as the home and garden one alone is not really useful for every situation.