The humane society has no authority to do anything on their own. While they do investigate animal cruelty, they have to get law enforcement involved to legally take any action. The time and manpower involved, means that only large scale animal cruelty gets investigated. Puppy mills, dogfights, that sort of thing. They would need an immense amount of resources to investigate every complaint about a single bird or overstocked fish tank, and they'd still need to get law enforcement involved, which for the purposes of single pets or tanks, simply isn't in the budget, nor would the majority of taxpayers be in favor of it being included in the budget.
There's also a huge difference between ignorance and abuse. There are far more fish tanks out there that are grossly overstocked or disease ridden than there are that are properly stocked and healthy. Most of the owners of these tanks aren't doing it on purpose, they simply don't know any better. They believe that the sign that says "small" at the pet store means that the fish will stay small. They have no clue what a nitrogen cycle is. They clean their tanks by taking everything out and cleaning it with soap. They don't do water changes, but instead add cold untreated tap water when the tank looks low. They don't do these things with the intent to harm their fish, they simply don't know any better. The pet stores don't tell them how to care for the lives they are selling them, simply because sales would be severely reduced. People would learn that they couldn't keep the kind of fish they want without huge tanks, and even small tanks require more maintenance than they'd care to do. On top of that, the employees are often ignorant themselves, like the Petco employee that tried to tell me that the first step in the nitrogen cycle was when the Ph in the tank goes down. My point being, that while these people do keep their fish in terrible conditions, they don't know any better. Most of us were in the same position when we first started keeping fish. The difference being that instead of selling off our tanks and equipment after a few failed attempts at keeping fish alive, we chose to research the cause of the problems, and try again, eventually gaining the knowledge and experience to keep our future fish happy and healthy. Before the internet, even doing that much could prove difficult. Even with the internet, there's often as much misinformation out there as there is accurate information.
In an ideal world, no one would ever accept responsibility for the life of any animal without the knowledge of how to properly care for it. The reality is, they don't. But it's not right to sick law enforcement and animal rights groups on people simply due to their ignorance. In many cases, simply approaching these people, and without laying blame, offering them the knowledge that you have to share, can be more than enough to solve the problem. Even when it's not, sometimes you have to realize that the world at large doesn't see animals the same way that you see them, and come to terms with the fact that often you can only save/be responsible for the lives of animals which you have personally accepted responsibility for.
