Pond Boss Forums MANAGING AN EXISTING POND Fertilization Algae bloom help

Catmandoo is doing a pretty good with answers so you don't need a lot of others saying basicially the same thing. Blooms with green water can continue into winter if ample nutrients are present, although the algae species my change as the temperatures and daylengths change. Thus the bloom water color / hue may change somewhat.

Often in managed fertilizer added systems, one stops fertilizing in mid to late summer and available nutrients get consumed before winter and water clears up as bloom dies off. In "natural" unmanaged systems there is often a weak or mild fall bloom which consumes most of the available nutrients - maybe during or after the fall turnover. Often the nutrients are not replentished in real late fall, early winter, so the water clears after the fall bloom dies out when most all nutrients get consumed. Blooms of certain cold water algae species can occur under the ice - cold tolerant diatoms are often the species doing the under ice blooming.

IF the pond is static (no outflow) pond dye can help slow the bloom. Sometimes light doses of algacide or spot treatments (small areas) can help suppress blooms. Care has to be taken not to kill too much bloom and cause a DO loss.

Main problem of too big of a bloom is a string of cloudy or rainy days can result in all that bloom not getting enough sun light and algae consumes more DO than it produces - fish kill then happens usually late night very early morning - 2-5am. If strong aeration is present then a fish kill can often be avoided during heavy blooms and dark days. When all of the bloom dies all at once (runs out of nutrients) then a DO loss can also occur when all the dead algae rapidly decomposes.