* Nutritional Deficiencies: Feeding blocks often lack the variety of nutrients that fish need for optimal health. This can lead to deficiencies in vitamins, minerals, and other essential nutrients, which can cause health problems such as stunted growth, weakened immune systems, and disease.
* Overfeeding: Feeding blocks can be difficult to control, which can lead to overfeeding. Overfeeding can cause a variety of health problems, including obesity, digestive problems, and water pollution.
* Water Quality: Feeding blocks can dissolve and release nutrients into the water, which can lead to water quality problems. This can cause stress and health problems for your fish.
If you are going away for three weeks, it is best to have a friend or neighbor come and feed your fish regularly. This will ensure that your fish get the proper nutrition and care they need. You can also consider installing an automatic feeder, which can be programmed to dispense food at regular intervals.