Brakish tanks, although harder than freswater are definatly as hard as pure saltwater. You need to remember when topping off the tank not to add salt. However when taking out and adding new water you need to add salt. In a 10gal you could try some bumble bee gobies. They are small and will live in caves and overhangs. With some skill and some luck you could breed them. For the top you could add mollies, or guppies, or platies. Really and livebearer. Good luck *crazysmiley*