Trout Feeding

Curious about what to feed your trout?  Which brand of fish meal is best?  A recent study by the Pennsylvania Fish and Boat Commission ranks Bio-Oregon as the best food for trout fry.

Feeding trout can be a difficult job when you're first starting out.  It's hard to know how much is too much, and how much is not enough.  Furthermore, it's dangerous for the fish to both underfeed and overfeed.  Underfeeding starves them so they cannot become strong, and overfeeding can lead to serious ammonia problems.  At the end of the feeding, the small fry should have full bellies, and in general your trout should look strong and healthy.

There is a detailed set of guidelines below.

A summary is as follows:

  • Swim up stage -.01 ounce of food per fish ( times number of fish) (for How long? until most reach 1 inch in size)
  • 1 inch or or more in size -.05 ounce of food per fish - multiply by number of fish (switch to size 1) 
  • More than 1 1/2 inches - .12 ounce per fish - multiply by number of fish (switch to size 2) 
  • More than 2 1/2 inches - .38 ounces per fish - multiply by number of fish.

It is also important to clean up any leftover food after every feeding.  If you see leftover food after about ten minutes or so, use a net or vacuum to take it out of your tank.  Replace any water you've lost in the cleaning process.

Trout Feeding Guidelines
By Scott Covert, Debruce Hatchery

Your food comes in three different sizes...smallest to largest, 0 to 2. Start feeding with the bag marked 0's, then 1's, then 2's. The food is perishable, so keep the bags sealed and in a cool, dark place, a refrigerator if possible.

First Feeding: Size 0 (meal)

Timing: Your hatchlings do not require feeding for 7 to 14 days after hatching. They will feed from their yolk sac as they stay low, at the bottom of the hatching basket. When you see the first hatchling begin to rise off the bottom of basket, you can start providing miniscule amounts of food. Much of this first food will go un-eaten, but by providing it to the developing fish, it will be there when they're hungry.  This is important.  Food must be available to fry when they first want to eat.  However, you must also remember that at first they are feeding on microscopic organisms in the tank that we cannot see or detect.  This will provide some of their early nutrition.

NOTE: There WILL be a small mortality rate as the fish start to feed...some hatchlings just never begin eating, and pass away.

When your fish reach about 1" in length, it is time to switch to Size 1.

When your fish reach about 1 1/2" in length, it is time to switch to Size 2.

NOTE: Because it is easy to run out of size 2 food at the end of the year, and because size 1 and size 2 are about the same, we recommend finishing size 1 before moving onto size 2.

Quantity: When born, your hatchlings are very small. Assuming 200 baby fish feed them approximately the following amount of food each day--interpolate as needed:

  • First feedings, fish still in hatch box: feed very little food.
  • Fish just out of hatch box: 0.34 grams (0.01 oz) of food.
  • Fish = approx. 1": 1.36 grams (0.05 oz) of food. (Switch to size 1 now).
  • Fish = approx. 1 1/2": 3.4 grams (0.12 oz) of food (Switch to size 2 now).
  • Fish = approx. 2 1/4": 10.9 grams (0.38 oz) of food (Fish ready for release).

Many teachers prefer to feed their trout very small amounts of food a few times a day.  You can easily divide the daily amount over two or three feedings.

NOTE: You can calculate feeding amounts quite precisely, but this is unnecessary. The formula is below for those if you are interested.

The 0's and 1's need to be sunk down to the fish, because the oil added to the food will cause it to float. A small plastic paddle will work fine. When the food is introduced to the water directly above the fish a slight back and forth motion should get the food to sink.  It is important NOT to overfeed your fish. Wasted food will degrade water quality. If you start to see clumps of dull yellow forming on the bottom or sides of your tank, gently remove it with your net. You can also use a small siphon, but use care not to suck up your "kids". When the fish get larger and you switch over to size 2, you will be able to see them actively feeding more than you will with sizes 0 and 1.

  • Be sure to take out dead fish.
  • Keep your food in a dark place out of direct sunlight (in a refrigerator, if possible).
  • When you are about to run out of one size of food, mix a little of what's left into the next size larger before switching.
  • It is better to feed less food, more often, than a lot of food all at once.

A Note About Enthusiastic Help:

Every year, many schools enlist the assistance of security and maintenance staff members to feed the fish on the weekends and holidays. They, as most of us, often become great fans of the fish, and are soon spending their breaks watching...and yes...feeding the children. People with different schedules, feed the fish unaware that others are doing the same. You might want to warn these fans about over-feeding and have a sheet of paper near the tank so they can track how often the fish have been fed.

Calculating Food Quantity:

The formula is simple.

-------- x 0.03 = weight of food needed to feed fish in POUNDS

P = Number of fish per pound
N = Number of fish in tank


At birth, your fish will weigh about 8000 to the pound. If you started with 200 eggs, they will require only 0.012 ounces or 0.34 grams per day. They will reach about 1" before you need to move up to size 1, by then they will weigh about 2000 to the pound (bigger fish, less per pound), and will require about 0.048 ounces or 1.36 grams of food.

Approximate number of fish per pound...based on average length:

At Birth: 8000
At 1": 2000
At 1 1/2": 800
At 2 1/4": 250

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