This is something of a debatable point, and a couple of us engaged in a discussion on this very fish a few weeks/months back. You need to know the source of the fish. If they are wild caught, they will not survive more than a few weeks in hard water, which is anything above pH in the 6 range, and hardness above 5 dGH; slightly higher hardness may
If on the other hand the fish are tank raised, according to some experienced aquarists they will manage well in similar water as they were raised in. However, knowing the pH and hardness of the source locality of tank-raised fish is not always a simple matter; many are raised in outdoor ponds in SE Asia and in tanks in Europe, and some in Florida. The fish from Asia will have been raised in soft water in all likelihood.
Another important issue with water parameters is temperature; the Blue Ram
] is a warm water fish, 82F or higher. Not all tropicals will last at such temperatures, so your tank companions have to be carefully considered.
The Bolivian Ram
on the other hand is much less demanding, and quite adaptable due to its varied natural habitat. Hardness should still be on the soft side (up to 12 dGH), and pH can vary from acidic (5-6) to slightly basic [up to 7.8] and they do well at normal aquarium temperatures around 77-79F so easier to manage in community aquaria. More info on our profiles, just click on the shaded names.