John: Rarely, if ever, is Cutrine's dosage based on the size and depth of the pond; despite the fact that the dosage for several other aquatic herbicides and lake-dyes are indeed based on the BOW's volume.

Instead, treatment-rates for Cutrine are based primarily on the surface-area and depth of the "targeted areas". The product's specimen label is rather vague in this respect and needs some interpretation.

By label, the liquid formulation of Cutrine should be applied at .6 to 1.2 gal per treated acre-foot of water. In reality, 99% of liquid-treatments are applied to shoreline areas where the water-depth usually ranges from 0 to 3'; so let's call it an overage of 1.5' in depth for this example.

Assuming the treatment of a 15' band along a pond's perimeter, it would require 2,900' of perimeter shoreline (x 15' wide) to comprise 1 surface-acre. Therefore, a 15' band x 2,900 linear-feet of shoreline x 1.5' avg depth = 1.5 acre-feet of water; x .6 to 1.2 gal of Cutrine = .9 to 1.8 gal of product applied within the designated area. Scenario-variations may fluctuate from this purely hypothetical exercise, but hopefully you'll get the general premise.

Cutrine's dilution-factor with water is somewhat irrelevant. In general, it doesn't matter if the calculated dosage is mixed with 10-gal or 100-gal of water-carrier ("diluent"). In either case, the same amount of actual product is applied to the designated/calculated area, with the only difference being the amount of diluent that's used in the process of distributing the product. In most cases, the treatment's performance is usually enhanced with higher volumes of diluent - since coverage and mat-penetration is aided by relatively higher application-volumes.

Granular Cutrine is a bit more cut-n-dried from a dosage-rate standpoint. The labeled rate is 60-lbs per treated surface-acre. Depth is somewhat irrelevant since it is assumed that bottom growths of algae are targeted rather than surface-mats.

Regarding when to use which formulation: It is far better (from many aspects) to target bottom-growths of algae (i.e. the nursery) with the granular formulation - before the algae colonies release and float to the surface where they usually form massive mats. These mats may be treated (sprayed) much more effectively with the liquid formulation than with the granular version, BUT always remember that the surface-mats represent mature colonies. Whether the surface-mats are treated/controlled or manually removed, they're likely to be replaced in short order by recruitment from the nursery-source on the bottom (wherever adequate sunlight is able to reach).

Lastly: "HOW MUCH to treat at one time?" is a question with lots of variables to consider. Ultimately, one would not want to treat "too much" algae at one time in order to avoid any potential dissolved oxygen (DO) issues. The size of the water body, the presence of aeration or wind-turbulence, the water's temperature and the degree of infestation are all factors that contribute into the equation of how much may be safely treated at one time. As a rule, treatments of low-density algae populations, in incremental portions and in cooler waters are the safER management approach if algaecides are involved.
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Zep - An "expert" is assumed to know everything about a subject. I certainly don't! Many of the so-called experts on this board have simply spent a lot of time learning as much as possible about their areas of focus - and we're the first to admit that it's a perpetual process which is greatly aided by sharing info between a lot of other knowledgeable people.

Kelly Duffie
Cypress, TX