It is very small. Very small. Besides the size, the concrete walls of the pool are rather uncompromising.
A week later we were at Cologne's new Hippo House - quite a contrast (although we were suprised that there didn't seem to be a pool outdoors at that one (massive one indoors, of course). I suppose they get more grazing space if they don't duplicate the pool.
Otherwise, the new Hippo house at Cologne Zoo isn't really much better. Its bigger, but not better, so the hippos do not have an outdoor pool, just for the reason, that the people can see them underwater in the house...Hippos are very easy to keep in human care, but no german zoo knows that and is keeping hippos in a really good way.