Well, I will not like to recommend the use of drug in aiding fish growth but will rather prefer giving you tips on some good management practices that can enable your fish grow faster especially with regards to feeding the fish with high quality feed of enough quantity.
Do regular sorting to reduce competition that may affect the growth of some fishes. These will help you have big and healthy fish rather than using drugs to make them grow faster.
However, all these are still subject to the quality of the fish in question because some fish farmers tends to make the mistake of buying fishes that are not of good breed that may not grow well probably due to the price at purchase or other cheaper means.
In this case, there is nothing that can make them change their genetic make up and allow them grow big over night which is why I will advice that you dispose them off because If you choose to keep feeding those fishes that you already know will not grow big, you may be running at a loss for the amount you will later sell them can never compensate for the amount in raising them.
There are several factors that affect the growth of your catfish. Growth of your fish and profit will depend on how efficiently you manage your farm, the water quality, disease control, and the number of fish you STOCK per ponds size.
Here is a list of other factors affecting your fish farm production:
Temperature
Pond PH Balance
Fish feed quality and right quntity.
Water quality (Dissolved solids)
.Sorting
Temperature
Catfish grow best in warm water between 83-86o F. You can begin spawning of your fish in the spring when the water temperature rises above 70 o F. You may collect juvenile fish from a nearby hatchery.
Flowing water
Catfish do not grow well in small ponds because of competition for space and oxygen. Catfish tend to grow faster when their is enough space. The bigger the spacing, the bigger and faster they grow.
Pond balance
Maintaining a balance in your pond is important because if you have fish growing in higher density, it could give rise to toxic water and pollution. Your fish will get sick and grow less. You must always maintain a ph of between 6.5 -7.5. Anything far or less is at your own detriment.
Fish feed
For rapid growth, use a nutritionally balanced catfish feed. I recommend skretting fish feed. Your catfish fingerlings will grow faster if you feed them regularly in the beginning of production season, they will grow the right size when you maintain this factors as stated. However, feeding too much will result in poor water quality and it will also increase your feeding costs.
Water quality & fish health
Water plays an important role in raising healthy fish. A water without dissolved harmful solid toxins or poisons is the best for your catfish rearing.
Your water should have a pH between 6.5 - 7.5. If the pH is too low, add limestone to your pond. Also check for dissolved impurities. Both physical and chemical factors play important role in rising catfish faster.