5 small fish in a 40 gallon may have room to increase his bioload and add visual appeal. Depending on his scape and filtration. There are often multiple methods for addressing tank situations in this hobby and each tank is unique so this affords the hobbies to choose what works best for their situation. As you gain more experience you will understand this better and not be shocked by informative responses you see....good luckI wouldn't add more fish to such a small display I was shocked to read that.
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