What to add

Nabster....they're interested in selling fish....they don't care what you have in your tank....at least that's what I have come to learn with these big mega stores. Basically, most of these stores will sell you anything you want....whether it's suitable for what you have or not.

Best bet is to always check out the fish you'd like...before you buy. I usually go to "Liveaquaria.com" to check on fish...but I don't go only by what they say. I just like the site because of the way they have it layed out. I pick fish I think I'd like to have and then do further research at other sites...and also ask here.

I don't know of any shark type fish that is suitable for a 10 gallon tank for any length of time. And the barbs aren't either.

For a 10 you can get a group of any of the smaller type cory cats, dwarf gourami, otocinclus, guppies, small to mid sized tetras, some species of shell dwellers, possibly one pair of dwarf rams..though they prefer a bit more horizontal space...and I'm sure there are lots more that others can add on to here. Some of these fish prefer to be in groups (tetras and corys)...others will be fine by themselves (dwarf gouramis, rams) BTW....not ALL of these fish at once..lol..just some examples of fish that will do ok in that size tank.

Anyway, lots to choose from for a 10......good luck chooseing...lol

The fact that you have two red tail sharks in the same tank for the same amount of time with one much larger than the other should let you know that some quarreling is happening. Fish act differently when they are being watched. If you one day turn of your room lights and observe the fish for a half hour or so, you might see a different picture. My shark appears to be the friendliest shy little fish on the surface but he likes to chase my poor fish all around the tank whenever they encroach on his territory. In a 10 gallon tank, they entire tank will turn out to be your larger shark's territory.

Just a general question... What do you mean you "got rid of" the smaller shark? Where do unwanted fish go? Did you bring it back to the pet store or something...? I've heard people talk about getting rid of plecos and such as well, and have always wondered what that really meant. o_o

yes, see if they'll take the fish back.... if not, find another LFS and ask them. If at first you don't succeed, try try again

I see you have learned that the term "petsmart and petco fish experts" is an oxymoron

Try to find a fish only pet store in your area. They will probably be more educated and helpful.