BARN: Fish


Goldfish in water troughs. Do they help, hurt, or does it matter?


There are two main benefits for goldfish in water troughs:

  1. Reduce Total Dissolved Solids.

  2. Reduce Mosquito and Fly population.

First, water quality is measured by Total Dissolved Solids (TDS). TDS is a measure of the total concentration of dissolved substances in the water, most commonly minerals and salts. The National Research Council’s Nutrient Requirements of Horses (2007) indicates that TDS levels less than 1,500 is considered safe for horses. Over 1,500 and diarrhea can occur or even refusal of water. However, water can be considered “safe” with a TDS of 6,500 p/pm.


Until very recently there was little to no data about whether goldfish impact water troughs. However, recently published work from researchers at the University of

Minnesota suggests goldfish can reduce TDS.


The researchers found for every degree increase in water temperature, TDS increased by 0.8 mg/L. All tanks with goldfish also had lower TDS levels than troughs without.


Second, mosquitoes like to lay their eggs (about 100 to 300 at a time) in a dark spot in still water. The eggs then float on the surface of the water for about 48 hours before hatching into larva. The larva will live in the water for about 10 days. It then changes into a pupa that floats on the surface of the water for about two days before the adult mosquito emerges.


The goldfish feed on the larva before they get a chance to mature, which can greatly diminish the mosquito population near your horses without any chemicals or pesticides.