Hippo water is almost always dirty, even in more modern exhibits with massive filtration systems. Hippos mark their territory by spraying faeces, after all...
The thing you have to understand about hippopotamus is, they defecate. A LOT. Roughly once or twice an hour. And they do it - and this is the important bit - in the water. In other words, even a collection that cleans the hippo pool once or twice a *day* will end up with a pool looking much like the above photograph on a daily basis.
This, incidentally, is a good demonstration of why my advice in the guinea pig thread - do your reading on a topic before commenting on it - is good advice!
You seem to have negitive comments of at least posts, may i suggest do some homework on the animal or exhibit before committing, or you may find some members may not be so polite on the comments you recive
