I also want to add that if you do have soft water fish, such as discus or SA cichlids that require softwater, you may want to look into an RO unit. Water softeners work by replacing minerals in the water with salt, and if your starting with extremely hard water, it is possible to wind up with water that is too salty for your fish.
I would recommend tapping into a line before the softener. Often the outside faucets are not softened as it saves on salt usage for yard and garden which don't need soft water. Since there is no need of soft water for most fish, using it would not be an economical way to go and if you are dealing with fish that require hard water, it is definitely the wrong way.
Sorry, but the comment about replacing minerals with salt is not true. While the unit does use salt, it is an ion exchange and the salt does not wind up in the water. It is used during a flushing portion of the cycle and runs down the drain. Technically there is some salt left in the water as it is not possible to rinse all of it out of the resin but the amount left in the water is equivalent to what is found in a slice of white bread. Common misunderstanding of how softeners work. The only time one would get salty water is if he uses water during the flush and rinse cycle. Those are normally timed to occur when people are not using water. Normally 2AM is standard unless lifestyle requires a change in the schedule.
So you would agree that folks are not drinking salt water or anything close? There seems to be a lot of confusion and misinformation floating around about softeners. I have nothing to gain or lose on the deal but I bristle when the facts are so missing. The process is much the same as what goes on in the dishwasher with soap. The soap is used to clean the dishes in much the same way salt is used to clean the water. Both are then put down the drain. We have to admit that there is some of each still left but that's not like calling it soapy or in this case salty. I think it would be more correct to say that the sodium ions are exchanged rather than saying sodium is placed in the water. Swapping ions around is harder to understand but a whole lot different than leaving the impression that all that sodium (salt) is placed in the water. With all the real health hazards to worry about, I hate to see another meaningless worry added to the folklore.
I'm not going to carry this argument on forever, I'm not saying a water softener is going to turn your tank into a marine environment, What I was saying is they add a measurable amount of salt, that owners of finicky fish, such as discus, may want to avoid by opting for a reverse osmosis unit
I actually use tap water after the softener. While the tap is indeed, softer than the well, it is not soft by a longshot. We have "liquid rock" around here. If I fill the kiddies' pool from my un-softened water, I get a tremendous amount of mineral sediment and iron staining, so I have to imagine I wouldn't want that in my tank. I did start adding Epsom salts to my water changes when I set up a Tang tank, and do that for all my africans now.
I know I'm new here, but about 10 years ago I had 16 tanks full of mouthbrooders and their fry. I use the water straight from my tap. My well is only 180 feet deep. Water from my tap has a tds level of over 700. I would never use the water before my well system, on any given day, only God himself knows what's in that water. I know when my water system is down, the water stinks, is filled with iron. Just the sulfur smell alone would concern me.
I have a water softener, and I go after the softener, from the tap.
I found not having to worry about any chlorine/chloramines, or any bad stuff makes it heaven doing a water change.
I would much rather add epsom salt than worry about adding prime to detox the very water I'm adding to the tank.
My wife doesn't have discus, but she does have angels and while it hasn't been a perfect run (we've lost 2 in 6 months, but I think I scared one to death and I think the other was bullied), all 9 aquariums seem to be doing very well.
That being said, we don't have any live plants in our tanks. I tried raising anacharis (who can't do that?) but it kept dying off. Could have been the temp though; I heard it only likes colder water and it was in 80Ã‚Â°F.