Saltwater tanks are beautiful, but they are extremely sensitive to many different water qualtiy dimensions, most of which have long time constants. It is not just about the chemicals taking time to dissolve. It is a living *system* with complex interactions that show up as long term trends. There are many different adjustments and any of them are suseptible to over control. Diagnosis can be tricky, and reaching a relativly stable equilibrium can be time consuming. Most people seem to over control their tank and kill all of the inhabitants. Disease can also be an issue especially when introducing new fish, but IMHO, not knowing how to work with gradual, long time contstant changes is the bigger problem.

Certain marine animals, notably octopi, are so sensitive to water qualtiy it is almost impossible to keep one. A good dealer will know which animals are easiest to keep (generally, docile and less sensitive to slight changes in water quality).

People also get too many fish for their tank. Salt water fish require substantially more space than most fresh water fish, and the requirement is often expressed in "inches per gallon", which is how many inches of fish length each gallon in the tank can support. It is a surprisingly small number, which (I'm guessing) is why others have said to get the largest tank you can possibly afford.

You need to carefully consider which animals will be in your tank. It is *very* easy to get a combination of animals that will not peacefully coexist, as was mentioned earlier in the story about the crab. The classic combination of clown/anenomie is wonderful and they work together beautifully. Other great combinations are out there.

Let's see...other thoughts: do your research and find a dealer that only does marine aquariums and has been in business for a long time.

Find and read: Nick Dakin's "The book of the Marine Aquarium", which is the bible of the subject.

Finally, choose either a reef tank or a fish tank. Although it is possible to have both types of animals in one tank (and they are stunning), it practically requires a degree in marine biology. I'm not kidding. A "reef tank" is a tank which contains "live rock" which is living coral and other invertebrates.

I don't do this any more because I like to travel and I don't like all of the maintenance and cleaning. You can pretty much forget about an away from home vacation of any length. If you are a neat freak, don't travel, can comprehend complex, multivariable, long time constant systems, and are willing to read and study, then it can be really awesome. I once had a blue damsel that would eat from my hand. Because they are so beautiful, I find it much easier to become attached to marine fish than fresh.

FWIW,

Jim