O.k., I know I already posted once, but I'm going to post again. No matter what you tell customers about how many fish can go in their tanks, your tanks will be overstocked. At my store we used the overused/not always right "inch per gallon rule". I always told them, that it was a rough rule, and worked best for small fish. (for example, ten one inch fish would be happy in a ten gallon tank, but one ten inch fish, while technically fitting the rule would not be happy because it would have no room to swim). Also, fish that grow tall, rather than long, like angel fish, take up more space per inch than fish that grow long but not tall. So, I would tell them this. But, I would always have some customers ask me how many gallons one of our tanks was. (they were challenging me b/c it was obviously overstocked). I would reply, "I don't really know, but our whole fish system is about 3,000 gallons. We have lots of extra filtration, and the way our filtration works, our tanks are continually undergoing a water change, and our fish are not in their permanent home, but are only here temporarily. But, I would get some customers who wanted to stock their tanks as full as ours.....
Emily