My experience of altums was from having them in an aquarium shop where i was working so i havn't personally kept them at home long term.

In general though i think most fish species, within reason, are quite flexable in terms water conditions (temp, ph, hardness etc.) especially if acclimatised. I think there is often a tendancy in fish keeping to focus very heavily on water parameters and perhaps not pay enough attention to other important asspects such as feeding and minimising other stress factors. I think what Tom said in terms of feeding and giving them somwhere to hide is very important.

The state that fish are in when you get them is also very significant. Important factors here will be things such as:

Disease: fish that have been recently moved (perhaps a number of times) are likley to be stressed and more suceptable to disease. Wild caught fish in particular may have internal parasites that may not normally caused problems but when combined with stress and poor nutrition can cause problems.

Condition: If a newly obtained fish is very underweight it can be hard to tern this situation around (points given above for disease are relavant here).

Genetic quality: For captive bred species, especially those that have been produced comercially for a long time, then genetic quality is a real issue (this probably won't apply to your altums).