Discus Fish Grow Faster in a Smaller Aquarium

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 *In my many years of growing Discus fish to adulthood, I have repeatedly found that they grow faster in smaller aquariums rather than large aquariums. I believe they simply burn fewer calories in a smaller tank due to lack of area to swim, which results in them growing faster and larger. You may wonder, why do they grow so large in the wild? My belief, is that they have an abundant supply of fresh water and food, which in an enclosed aquarium environment could not be simulated without polluting the tank water. Another benefit to growing Discus in a smaller aquarium is that they grow more uniformly. In a bigger tank the dominant and most aggressive Discus gets all the food and outgrows the rest. This results in uneven growth rate within the school of Discus fish. Some believe that this uneven growth is due to hormones secreted from larger Discus in the aquarium stunting other Discus in close proximity. I do not believe this is true and have not seen uneven growth when grown in smaller aquariums.

I use only twenty, thirty, and fifty-gallon tanks. The 50-gallon tanks are for young adults which are 4 inch and up. The 30-gallon tanks for large broods of 60 fish in each tank until they are 2 ½ inch, then I split them into two 30-gallon tanks. I use 20-gallon tanks for breeding tanks and to house up to 20 babies 2 ½ inch Discus fish. By raising the Discus fish in these smaller tanks, I achieve uniform and faster growth. A 2 ½ inch discus fish is only three months old when they are shipped to customers. The growth rate from 2 ½ inch to 4 inch keeping the fish in a small aquarium will only take four more months. If I were to raise the same fish in 100-gallon tanks their growth rate would be cut in half, and it would take eight months to a year to get up to the same 4-inch size. There would also be uneven growth rates, as the dominant fish would get more food and outgrows the rest. Whereas, in the smaller tanks at 4 to 5 months of age the Discus would show minimal size differences amongst the group.

The amount of the Discus fish in a school will also determine how evenly they grow. The larger the group the more diluted the pecking order and more uniform their growth will be. I do not believe, and do not follow the rule of thumb whereby one Discus should get 5 to 10 gallons of water. Instead, I stock my tanks with more Discus fish until there is no visible pecking order. This will ensure that at feeding time all the fish will get a chance for food and therefore grow at a uniform rate. Discus fish like a fresh tank and weekly water changes of 25% is what I suggest to customers. A good school of adult discus fish in a 100-gallon aquarium would be 30 to 40 adult Discus, in a 50-gallon tank would be 15 to 18 adult fish, and a 30-gallon aquarium 6 to 8 adults, the more densely populated the more diluted the pecking order.

Temperature is also important when growing out Discus fish. The warmer your aquarium, the more this will stimulate appetite, the fish will eat more and grow faster. I tell customers that in an un-planted aquarium to keep their temperature between 86 and 88 and a planted aquarium with adult Discus fish, keep this temperature between 84 and 86. This will enable the plants to thrive and the Discus to maintain a healthy appetite.

If your goal is to grow big Discus fish, start them in small tanks and as they approach 4 inches after a few months they can be moved to bigger tanks. I emphasize the trick is to start them in small tanks to restrict movement and excessive calorie burn. I happen to stumble on this method years ago by mistake and it has worked well for me ever since.

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