KEEPING A CLEAN TANK
Start with a clean, empty tank for each new delivery of minnows. Dry tank thoroughly or disinfect with a household bleach solution of 2 tablespoons bleach for every gallon of water. If you use bleach, rinse the tank well and use de-chlorinator chemicals when you re-fill the tank, even if you fill with well water.
USE CLEAN WATER
Remove chlorine from tap water using a commercial product. Most municipal water supplies contain 0.5 – 2.0 parts per million residual chlorine, which is toxic to fish. Aerate water before adding fish.
Minnows are usually delivered to you at 55 to 60°F. Keep the holding tanks in the shade, preferably in an air-conditioned location. Tank water temperature should be 65°F or below.
Constantly agitate holding water to add oxygen and remove carbon dioxide. Use air compressors, blowers or hanging agitators to keep the oxygen level above 4 ppm. Systems producing large clouds of tiny bubbles are preferable. The agitation should not be so strong that the current tosses fish around.
TEMPER NEW FISH
Fish are cold blooded. Rapid temperature changes are very harmful. Measure transport tank water temperature when fish arrive and try to match the holding tank temperature to it. Adjust the water temperature by adding ice, made from water with no chlorine or use de-chlorinator along with the ice. Water temperature should be changed by no more than 10°F in a 20-minute period.
When new fish arrive, add 1 cup canning salt or stock salt for every 20 gallons of water in the tank. Avoid iodized salt or salt with anti-caking additives such as yellow prussiate of soda.
WATCH LOADING RATE
Generally, don’t hold over 25 pounds of minnows per 100 gallons. For best care, limit the loading rate to 8 Ib per 100 gallons. The more pounds of fish, the more frequent water exchanges required to keep ammonia levels down.
Routinely check chlorine, pH, and ammonia. Check more frequently when tanks are heavily loaded or if a problem is detected.
Ammonia is the main fish waste product and even small amounts are toxic to fish. To control ammonia levels and reduce fish stress exchange water daily or twice daily. Drain tank to 1/4 volume and refill with fresh, chlorine-free water or add de-chlorinator chemicals while filling. Add 1/2 cup of salt for every 20 gallons of water that you drained and replaced.
REMOVE SICK AND DEAD FISH
Sick and dead fish are unsightly, spread disease and contribute to poor water quality. Examine holding tanks several times a day and remove visibly sick and dead fish.