Fish emulsion and seaweed extract are commonly used by organic gardeners but I use them too for plants in coconut coir. It adds or helps encourage the growth of beneficial bacteria and fungus in sterile potting mixes, as well as adding trace elements for the plants. The drawback is it stinks and you need to shake the bottle well before using it to get the sludge on the bottom back into suspension. Great for attracting flies in my area.
Mine was 0-10-10 and used to use it when feeding in flower. I have half a bottle left, but switched my whole line to AN products. I never had any issues other than stank.