I agree with the idea that people should pay more attention to how animals are treated and try to reduce the suffering experienced by animals. But, unless you are vegetarian, it is impossible to grant animal rights to all sentient beings. What is more likely to happen instead is that people draw their attention only to those animals that they feel close to or familiar with. Those who love dogs naturally emphasize how dogs should be treated. Those who enjoy whale watching might feel uncomfortable observing Japanese scientific fleet crossing the ocean and hunting whales. Such preferential attitudes might appear hypocritical to those who happen to be involved with particular animals. They might feel "why are you suddenly talking only about whaling while neglecting other animal sufferings including the animal which you had for lunch today?"
My personal feelings on animals and rights in general is this: All animals are equal and so should all be treated equally and well. I don't believe it is wrong to kill an animal for food, however i do think that animals raised or hunted for food should be treated well and have their basic needs attended to properly (like decent amount of space to roam in, good diet, clean living quarters, animal not kept in isolation if it is sociable animal etc), and should not be caused to suffer unnecessarily (for example when the animal's time is up, it should be killed in a humane and attentive manner, even if it is more costly to do so).
If all animals were treated this way, then much of the cruelty involved in the animal human world (for example like in certain farming industries) would be immediately eradicated. Unfortunately though a lot of people put profit before animal welfare and so the animal suffers throughout its entire existence (which is highly immoral/wrong).
But, I'm curious why we are less critical about how fish are treated. Peter Singer mentions our insensitivity to fish that fish are normally slowly suffocated when they are caught. The same Japanese person who will be disgusted to witness some animal being slaughtered does not necessarily feel ill to see some fish moving its mouth at the edge of his plate or might enjoy such a scene as a sign of freshness.
Yet, again this might be a cultural issue. Ordinary Japanese do not feel comfortable seeing a chicken sold with its head still attached, but Chinese people display the opposite reaction: appearing tasty.
I think a lot of people are insensitive to fish because a lot of people are unfortunately very ignorant about fish and believe them to be on the same level intelligence and feeling wise as that of insects, mollusks, bugs etc.
I think a lot of people see the fish more as an object, a piece of food (like those Asian people who like that "live fish on the dish" sashimi meal), rather than a living, breathing, feeling creature.
Ordinary Japanese do not feel comfortable seeing a chicken sold with its head still attached, but Chinese people display the opposite reaction: appearing tasty.
I think that is possibly because;
a. The Japanese don't like seeing the head on the animal because it makes the animal seem more real to them- the Japanese (like many other people), like their ham to look like ham and not look like a pig. Any indication that the meat was once a cuddly living animal makes the meat-eater in question feel guilty and very uncomfortable.
Personally, i don't think such people should be eating meat at all- if you cannot properly and comfortably come to the terms with the fact that what you are eating is an animal, then you shouldn't try and hide in denial and continue to eat.
I personally believe that the decision to eat meat should not be one that should be taken lightly or ignorantly- eating an animal means killing it, and to kill anything is a grave matter. If you don't know where your food (i.e. animal produce) comes from and how it is prepared, then you really shouldn't be eating it, because otherwise how can you say that you've really thought through what you are doing when you are choosing to live in partial ignorance about what you are doing?
I eat meat, not often i admit, but i have no gripes about killing, preparing or eating an animal. I do however care massively how the animal i eat was raised in life and killed- i am against practices that cause the animal unnecessary suffering (like battery and 0 grazing farming). This is my moral decision i have undertaken- i want to know where my food comes from, what it was and how it was prepared and i know i can handle this and i don't feel uncomfortable about doing it.
b. The Chinese: I believe the Chinese in the case don't feel uncomfortable about the head on the chicken like the Japanese do purely because their animal culture is still one where animals are viewed as commodities, objects, investment etc and nothing more.
The Japanese live in a culture where they are (literally) generally very far removed from the animals they eat- farms are kept on the outside of cities and towns, out of sight of where people live. So there's not much in people's lives to be reminded of food animals or to learn from them etc.
In this animally sterile environment, the cutism culture fills its place- people are surrounded by cute pictures of everything everywhere, and this includes cute pictures of animals. The Japanese love the cute pictures of chicks, cows and horses, but these pictures are not realistic and are often far removed from the real thing.
So the Japanese would have no problem seeing a cute picture of some happy chicks and chickens on a box of chicken soup noodles, because they don't really relate the cute pictures to actual animal they're eating- and besides, the pictures look cute don't they? (egg/chicken rice seasoning/furikake);
Don't the hen and chicks look so happy in their picture? Isn't it blissful?
So when confronted with the real thing;
This shatters the cute distant blissful ideal the Japanese in question has going on- they don't want to see a dead unhappy looking chicken, all they want to see is some nice nondescript prepared chicken in a packet with some happy cute pictures on it; they don't want a sight that makes them feel guilty or uncomfortable with what they want to eat.
The Chinese do have a cute culture of sorts, but its more recent and nowhere near as ingrained into society as it is in Japan. Animals in China are generally still pretty much at the object/item stage in terms of worth. The Japanese are at the animal fantasy phase, caring about animals but also largely living in ignorance of them in a very farm animal removed society. We in the west are in different phases at the same time (in fact everyone is going through the different phases everywhere) but also a 3rd phase- the realization of what the animal really is and are beginning to come to terms with it and try and work our morals around animals, which has spawned a whole load of different groups of people trying to come to terms with animals ethically/morally in their own ways (like the vegans, vegetarians, hardcore meat-eaters etc).
Anyways, its just a theory as to why the Japanese feel uncomfortable with the chicken with head attached, and the why the Chinese generally don't
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Education, education, education....
! Since the tank has not had a water change for so long, you don't want to shock the fish too much by doing a massive one, so just do a few small ones over the following days- the fish will really appreciate it 
