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3.3. Amount of Fish Food

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Author : David Bogert

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4 minutes
The amount of fish food to add used to be very important in the hobby. When I started in the hobby many years ago all the small guides I bought in my fish store, the small “Your First Aquarium” books, emphasized that the newcomers tended to vastly over-estimate the amount of food fish should be fed. The “guides” all emphasized restraint with the food. Since uneaten food giving high bacterial counts in the water is probably the number one killer of new fish this was a very good caution.

The guides I see on line now don’t make that caution. Since this is extremely important I find that somewhat confusing. If I hadn’t had that caution drilled into me early I think I would have lost a lot of fish and probably not stayed in the hobby.

picture of an aquarium fish Pseudotropheus Crabro
Pseudotropheus Crabro

The biggest mistake beginners do is to over-feed their fish. The directions on the food are ridiculous. “two to three times a day an amount they can eat in two minutes” is WAY too much food. Fish are coldblooded creatures and only need small amounts of food once a day. They should be fed an amount equal to two eyeballs per fish once a day. This is not a lot of food!

1% per day translates to this amount by the size of the tank:

Aquarium sizeAquarium sizeLight stockingModerate stockingHeavy stocking
10 gallons38 liters0.07 grams0.2 grams0.7 grams
20 gallons76 liters0.14 grams0.4 grams1.5 grams
40 gallons151 liters0.28 grams0.8 grams3 grams
80 gallons303 liters0.55 grams1.6 grams5.5 grams
100 gallons379 liters0.7 grams2 grams7 grams
Amount of dry food per day

This is a very gross approximation. Calculating the total weight of the fish in grams and dividing by a factor of 100 to 50 is far more accurate. But it is easy to use.

Another good rule of thumb is to simply add up the sizes of each fish’s one eyeball and feed and amount of dry food equal to twice that size once a day (six fish equals twelve eyeballs of dry food). It is a surprisingly accurate rule.

Vieja zonatus
Vieja zonatus

Note this is for a “typical” fish shape like a rainbowfish. If the fish is wide bodied like an Oscar or high bodied like a discus the numbers are obviously higher than the rough estimate.

The amount of food required typically needs a kitchen scale to be weighed out accurately. Sometimes five ten or twenty small piles will be required to come up with an accurate amount.

Note that many people assume fish must eat every day. This isn’t true as fish are cold blooded (poikilothermic). Aquariums can be left without food for up to two weeks with no ill effects what-so-ever. Of course, if you have juveniles and you want rapid growth, feeding twice a day is recommended.

When fish are first put into any aquarium, especially a quarantine aquarium, they will be traumatized and scared (especially cichlids). So, they typically don’t want to eat for a week or two. This is quite natural and don’t worry about it. Then it will take them time to get used to a new food. So, after a week or so, add a small amount of the food you plan on feeding them and then give them several hours to eat it.

Labeotropheus trewavasae Thumbi West OB Morph
Labeotropheus trewavasae – Thumbi West OB Morph

“Power Feeding”

Many people want to maximize their fish’s growth rate and they “power feed” them to grow them faster. This actually works! Fish do tend to grow at a speed proportionate to the amount of food they consume. So it is possible to feed a fish an amount of two eyeballs three times a day and one will get faster growth. But ONLY do this is you have a HUGE amount of mature biofiltration. By “mature” we mean a filter media that is loaded with beneficial bacteria and brown gunk that has been in place for several months without cleaning.

If one overfeeds without this mature added biofiltration your fish WILL get diseased. The number of newbies who do this “power feeding” without mature aquarium is downright frightening.

Piaractus brachypomus Red Bellied Pacu
Piaractus brachypomus – Red Bellied Pacu

Food in More Depth

There are some aquarium hobbyists who are interested in delving deep into the science and the calculations behind all aspects of the hobby. For those who are so inclined click on the following:

3.3.1. Amount of Fish Food in Depth

For those wanting more data on the many myths of fish food click on this link:

3.7. Banned Food

The myth of a correlation between high protein diets and Malawi Bloat is examined in this link:

3.8. Food and Malawi Bloat

Pseudocrenilabrus philander dispersus
Pseudocrenilabrus philander dispersus