Hard Water in aquarium

Question
QUESTION: How can I soften the water and is it necessary to do so in my tank? I also have a hard time maintaining my pH 7.0. After a couple days it wants to get very alkaline up to 7.5
I just keep using "pH down" and I don't remember having this issue with my 10 gallon. I have a 38 gal. now. I set it up about a month ago.I have also used a bacteria supplement for my environment which helped a little.

ANSWER: Hi Fred

What kind of fish are you keeping in the tank?  
Is the tank cycled yet?  
Also, with your 10 gallon, was it at the same house, using the same water supply?
One last question, for now anyway :), what is in the tank-gravel, sand, decorations, shells, rocks?  And if you know what kind of stuff-like is it lime stone?

Christy

---------- FOLLOW-UP ----------

QUESTION: 3 Silverdollars,4 Tiger Barbs,2 Red-tailed sharks,2 mollies
1 plecostemus. Different house.different water supply.
I don't think it is limestone. It is white gravel. I rinsed the gravel before putting it in. The tank was clear of cloudiness after about a week.

Answer
Hi Fred
I would say leave the ph alone.  Most fish at the stores are tank bred or farm raised, so they can handle most any ph from 6.0-8.0.  Discus and rams are pretty sensitive to ph and hardness/softness of the water, and trying to breed certain fish it's best to alter it, but in your case, they should do fine.  

The problem with those ph up/down chemicals, if you don't add anything in along with it to buffer the water, it just crashes or skyrockets back to where it was originally.  That is very stressful on the fish-called ph shock, and it can kill them as well.  A stable ph is much better for fish then one that fluctuates.  Here's a great link that talks about ph, gh, kh and all that good stuff that's involved with it, how to raise and lower the ph properly.  But again, I would just leave it alone:

http://www.drhelm.com/aquarium/chemistry.html

The only problem I really see, is with your sharks.  As they grow, they tend to get pretty territorial, with other sharks especially.  I have one in a community tank, he's about 4 inches or so now.  He's starting to chase off the other fish if they're in "his" area-which is pretty much the whole tank :)  If you just got them, might be a good idea to return one.  Here's a link with a little bit of info on them:

http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=1172

Hope that helps, and good luck!  Let me know if you have more questions!

Christy