My experience growing discus fish is that they grow faster in smaller aquariums rather than large aquariums. My reasoning is simply, they burn fewer calories in a smaller tank due to lack of area to swim in. Therefore one may ask, why do they grow so large in the wild? My answer is that they have an abundant supply of fresh water and food which in an aquarium environment could not be simulated without polluting the tank. Another benefit to growing discus fish 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 therefore outgrows the rest, causing an uneven growth rate within the school of discus fish. Some believe that this uneven growth is due to hormones secreted from discus fish stunting others in the same aquarium. I do not believe this is true, and have not seen uneven growth when grown in smaller aquariums.
Here, at Mac’s Discus I use only 20, 30, and 50 gallon tanks. I use the 50 gallon tanks for young adults which are 4 inch and up. I use 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 my 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 there 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. I would see uneven growth rates where the dominant fish which gets all the food and therefore outgrows the rest. Whereas, in the smaller tanks at 4 to 5 months of age the discus would show minimal size differences amongst each other.
The size of the discus fish school will also determine how uniformly they grow. The larger the school the more diluted the pecking order and therefore the more even their growth rate. 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 more uniform rate. Discus fish like a fresh tank and weekly water changes of 25% is what I suggest to customers. That being said a good school of adult discus fish in a 50 gallon tank would be 8 to 15 fish, the bigger the school the less the pecking order. In a 30 gallon tank I would suggest a school between 6 and 8, and in a 20 gallon tank 3 to 4.
Temperature is also very important when growing out discus fish. The warmer your aquarium is the more it will stimulate appetite; your 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 keep the temperature between 84 and 86. This will enable the plants to thrive in the discus to maintain a healthy appetite.
So, if you want to grow big discus fish, start them in small tanks and as they approach 4 inches in a few months they can be moved to bigger tanks. I emphasize the trick is to start them in small tanks to restrict their movement and calorie burn. Hope this blog helps I happen to stumble on this method years ago by mistake and it has worked well for me and will work well for you.
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