Types of Water to use for your tank. An analysis.

You canNOT use plain RO or DI water. It has no KH (stabilizes your pH) or GH (minerals, or hardness), and it probably has an acidic pH of 6 or lower, too low for most fish. You either have to treat the Deja Blue water with minerals and pH stabilizing agents or mix the RO water in a fixed ratio (50/50, 60/40, etc.) with tap water.

Here are some examples of chemicals that can be used to treat the RO (Deja Blue) water:
Seachem Equilibrium (adds minerals to the water, or GH-general hardness)

Seachem Acid Buffer

Seachem Alkaline buffer

I recommend reading through this website about water chemistry. Also try to find the range of general hardness (GH) that your fish will tolerate. For example this website includes that information. Use a KH, GH (general hardness), and pH kit for water testing.

I mix 80/20 RO/tap water to soften my very hard (dGH 18, dKH 13), high pH (8-8.4) tap water. (The water chemistry website from above explains this mixing practice.) The 80/20 mix results in dGH 5, dKH 4, pH about 7. My fish would probably be ok with conditioned tap water but it really bothers me knowing how hard it is. (If only I kept cichlids.)

By mixing the RO/Tap water I don't have to mess with chemicals (except for conditioner) to alter the water chemistry. My LFS sells five gallon jugs of RO water and Culligan sells RO/DI water at Wal-Mart for 27 cents per gallon. I will eventually buy my own DI or RO filtration system (not sure which I will choose) since that may be cheaper in the long-term. Some people use whatever comes out of their tap but I'm willing to put in a bit of extra work (and money) to make more ideal water conditions for my plants and fish.

Everyone has their preference, you just have to experiment to find out what works best for your setup (and budget).
 
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Tap water is actually ideal as the water a fish in the wild originates from has less filtration. Bottled drinking water has been filtered and sometimes it is nothing more than municipal water in a fancy package. That creates unneeded waste.

You actually don't want purified water for reasons already given. There are also trace elements present that help a fish's general health.
 
I believe San Diego has pretty hard water. You could mix 50% RO to your tapwater if you want to lower the hardness, although it really is not necessary with most fish. As others mentioned, it is not a good idea to go with 100% RO.
 
I was thinking about the fuji water. Just cause I'm a sucker for the square bottles. :lol2: Just kidding. My city water here is liquid rock and my fish seem just fine with it. Snails like it too. Its bad enough I have to CLR my showerhead every couple of months just to keep it spraying down, not out. No rust, thankfully, just pleanty of calcium and lime. That being said, I have never done and testing for TDS, or general hardness.

Sometimes it seems this hobby has the Wiley Coyote factor. Once the Road Runner gave him the book on gravity, he fell like a rock. Before that, not a problem to hang there in mid air for awhile. The more I stress about water parameters the more I seem to muck with things that are not as big a deal as people make them out to be.
 
Beachkrazed,
You're answer is what I was looking for. Just purchased an RO DI set-up with the intent of providing the best water possible for my fish. Before I add any of it I will get a hardness kit to better understand the water chemistry needs. I thought simple feedings of high protien foods would leach what was needed back into the water although that may be a misconception. Thanks for the input.
Cryo
 
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RO/DI is useful for topping off since the minerals are still present in the tank and you're just returning the situation to what it was before. The saltwater people use it all the time since they can maintain their salinity as the water evaporates, but for freshwater, bottled or pure RO/DI is very much overkill, and could cause problems depending on the source. I have to agree with the other posters and say go with good 'ol fashioned tap water with a good conditioner (I like Prime) and be done with it.
Being up here in the Northwest, we've also been getting hit pretty hard with "ban the bottle" campaigns as well since those bottles take quite a bit of water in the production and recycling process (if they're recycled), and often end up plugging up landfills. The brainwashing must be working since I'm starting to flinch when I see people with them now.
 
OK, OK, I think I'll do a little water testing first and make a better decision.
 
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