Originally Posted by bemaniac
Another thing... my LFS sells ocean water for $1 per gallon. They say it's ultimately cheaper than mixing my own SW. Is this true? roughly how much money (in salt) would it cost me to mix my own water?
This is simple. The salt mixes typically tell you how many gallons they are good for. I buy coralife buckets that are good for 150 gallons. Fish stores around me sell them for about $35 with tax. When you consider that it is possible to get an RO/DI filter for just over $100 I'd have to say your LFS is wrong.
For the original poster I say that for fish only, it doesn't matter quite as much. But I would still get RO/DI. And I wouldn't buy jugs or anything, I would get the RO unit. They pay for themselves pretty quickly. I probably bought $200 of water before buying my RO unit which cost about $200. By now I probably would have spent $500 on water.
One problem with tap water is that it could be inconsistent. You might have tested it on the best water quality day of the year. The quality typically fluctuates from season to season because the water company has to change the chemicals they add to the water to prevent algae and bacteria growth. Plus, SW fish have much higher demands than we do. I've tested my tap water before and it actually had some ammonia in it. Also, if you get a TDS meter you will likely find that your tap water has 200-300 ppm (of what, who knows). My RO unit brings that all the way down to ZERO!