RO/DI filter necessary?

[new2salt2]

I was just in my pet store and asking about a filter for water becasue i am going to start putting in soft corals. the shop owner told me that he just uses a regular tap water filter that filters out heavy minerals, clorine and alge producing bacteria. this filter is only 50 bucks and much cheaper than the 200 for an RO/DI.. i realize that most would stil use the RO/DI, but is it necessary? or can i get by with the other?

[Poseidon]

No replacement for RO/DI.... I think the filter he is speaking of, is similar to my Refrigerator's, it gets rid of bad taste, but not all the dissolved solids.