chris348,
Yes, that is possible to do if you want.
andywg,
No need to provide proof as it is a common fact that RO or RO/DI water with salt provides the correct balance of elements as found in natural saltwater. Just ask for a list of elements found in your tap water from your local water board and compare that with natural saltwater. There will be a difference.
Just because an animal spawns, does not mean it is happy as spawning can be a survival instinct. I am not saying it is not possible to keep marine animals in tap water, I am saying it is not the right thing to do when we can provide a better alternative. Yes, some areas have better water quality than others and people have kept marine animals in this type of water, I just do not believe it is right telling people it is OK to use it when RO's are available so cheaply. In my view, if anyone is concerned at the cost of water or the cost of RO untis, then they should not be keeping these animals.
We will obviously differ of this opinion but surly you agree it is our responsibility to produce the best conditions possible for these animals whose natural habitats are being destroyed daily. These animals are becoming endangered because of the destruction of their habitat so we need to keep the ones we have in the best possible conditions......maybe I am alone in this opinion in which case, god help the reefs!