So, are these coming directly from the exporter in South America, or have they been held for some time in a wholesaler's?
I would get a test-kit and see what the water condition that the fish is in at the moment. If it's similar to yours, you could just stick them in the tank [with the usual procedure of portioning some tank-water into the fish-bag to slowly fill the bag up with your tank-water].
I would also get a container of soft water, just in case they are currently in really soft water - you can buy RO/Distilled water in the supermarkets in the US. I don't know what the brand/name of it is, but I think you can find that out if you search this forum. Of course, your LFS will probably also be able to supply RO water for you.
If your fish arrives in really soft water, you would be best advised to set up a separate tank (temporary container like a bucket with air-stone and heater would be fine) and placing them in there. You can either slowly drip feed water from your tank to the temp-housing, or you can let them live there in the soft water, and doing water changes with harder water. After some time, the water in the temp housing would be close enough that you can move them to the "real" tank. Obviously, if you keep them in there for a longish period of time, you'll need a mature filter too...
As to bare bottom or otherwise, I don't see why that would make a difference - if you were to set up a special tank for these fish to quarantine in, I would have said to make it bare-bottom. But since you already have a tank that you can use, I don't see a reason to clean out the gravel. Only if these fish are dying from some strange decease would you need to sterilize/dispose of the gravel.
These are my personal opinions, and others may have other ideas. Listen to them too, and make your own decisions...
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Mats
