dd, I am guessing zebra danios, since they are amoung the most common.
A different site with a zebra danio profile lists their pH range going up to 8.0. In my opinion, the moral of the story is that not all the sites are right, and often are in conflict with one another. This is where some greater research is needed before you buy fish. Danios are usually some of the hardiest fish (a large reason why they have been used as 'cycling fish' for years) and should adjust to a pH of 8.0. Most fish that are not overly sensitive will (I'm thinking something like discus as a good example of a more sensitive fish, maybe some one else could chime in other examples).
But, as have been mentioned above, it is far far far more critical to keep a stable pH, than a specific one.
See, in order for pH down to work, you have to consume all your current water's buffering capability, so at first you will probably have to add a lot. Then when you get the pH where you want it, now there is no buffering to keep it there. So, the pH will drop over time from the nitrogen cycle. And you have to add pH down everytime you do a water change, and match the water change pH with the tank pH otherwise who knows what it will come out at. And, lastly, if the pH is moving around a lot = stressed fish.
So, keep it simple, look to acclimate your fish slowly if the store's condition are different from your tanks,
see this link, for example. and keep that pH constant.
well was i think its sorted now thanks to calcium plus 
