I see it as being no different to ringing the SPCA on animal cruelty or neglect.
I would certainly be trying to find out who services the Tank, as they clearly arent doing what they should be, isn't this a form of animal neglect too??
They clearly have the fish tank there for there customers to enjoy, who is going to enjoy looking at a tank in that state and think "WOW, what an awesome tank".
I say good onya puttputt for having your say, most people would just walk away on say nothing :an!gry