He has a 45 gallon tank the question is can a sene live in it for life.the answer is yes in fact a cpl of senegals would be fine.
caveat#1 your maintenence will have to be consistant
caveat#2 your water chemistry will need testing
caveat#3 there can be no other tankmates (45 gallons isn't sea world)
caveat#4 you filtration will need to be top notch-Anne