If you have never taken care of an aquarium then, I think you should start with a freshwater aquarium because you will get used to the water maintenance and if a fish dies then it will be less expensive to replace. Otherwise, if you have experience with a freshwater tank then you can just go ahead with the saltwater tank. That's just my opinion though. If you feel really confident in your research, then you can go ahead and start with the saltwater aquarium, but just be aware that the fish are more expensive to replace. Most fish stores near me don't offer the 14 day guarantee like they do with the freshwater fishes.
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Phishie

"An ounce of prevention is worth a pound of cure."