Mineral Supplement for Ponds #159294 - Ask Extension

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Mineral Supplement for Ponds #159294

Asked November 02, 2013, 4:13 PM EDT

The water in my pond is very clear and I have read this is bad. I have also read that I might need Diatom Algae to correct this problem and for food for fish. Can you give me some info on this and where I can buy or make my own ? Thanks in advance.

Cass County Texas

Expert Response

While clear water is not the best for developing a strong food chain for the fish in your pond, it is not necessarily bad. The best way to improve algal blooms and get some color in your water is by fertilization. Unlike terrestrial systems where nitrogen is the limiting nutrient, phosphorous is the limiting nutrient in aquatic systems because phosphorous precipitates, or settles out, of water. Phosphorous is the middle number of the N-P-K that you will see on fertilizer bags, such as 10-20-0. In this case, phosphorous makes up 20% of the fertilizer contents (indicated by the middle number, 20), so 10 lbs of this fertilizer will contain 2 pounds of phosphorus. The first question is, do you have a lot of aquatic vegetation in your pond? Rooted and floating vegetation including filamentous algae often lead to clear water in ponds. Why? Because once they become established they compete with the phytoplankton (microscopic algae) for nutrients such as phosphorous, and thus hinder phytoplankton growth. Before you ever fertilize your pond, you must first treat the existing rooted and floating vegetation. If not, you are only fertilizing the problem, making it worse and perhaps leading to extreme nuisance vegetation issue. After you have treated the existing aquatic vegetation, or have a new pond, freshly renovated pond, or a pond with extremely few aquatic plants, you can apply fertilizer. Without knowing the water chemistry of your pond, typically 5-8 pounds of phosphorous per acre will jump start a good algal bloom. Use liquid fertilizer or powdered fertilizer that is broadcast over the pond surface. Granular fertilizers quickly sink to the bottom where the phosphorous is locked up in pond sediment. The initial fertilization may need to be followed up at monthly to semi-annual intervals with half the initial application rate. Check the water clarity to determine algal bloom density. 18 to 24 inches of visibility is optimal for most farm ponds. Les than that, add fertilizer.  
Todd Sink Replied November 04, 2013, 5:47 PM EST

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