Did you dilute the liquid before applying, Mark? I've used liquid pond fertilizer in the past but the stuff I used was much denser than water and had to be diluted or it would sink to the bottom and go unutilized, i.e. give you no bloom; the particular brand I used stated this clearly on the jug. I just looked on Dunn's site and the liquid they sell is the same formulation as what I've used, and it also has the same recommended amount per acre (1 gallon), so it's a pretty good bet it has to be diluted. Ways to dilute include mixing ten to one with pond water and splashing onto the surface, or pouring the liquid into the prop wash of an outboard motor (the best method); you can also spray the liquid through a herbicide sprayer. If you used a liquid and didn't dilute, that may have been your problem. If the product doesn't state clearly on the label that it has to be diluted, that's on Dunn's or whoever makes the fertilizer.
Normally you should get a nice bloom within a day or two of application. If you did dilute the liquid and still have no bloom, your pond might be acidic and you might need to add lime. Have you tested the pH at any point?
