I have been looking at some fish to put in my new 55 gall aquarium, and I have found two fish i would like to buy, but first I need some answers. 1.) How do I get the right amount of salt in the water (because archer fish are brackish water fish.)? 2.) How many could I have in 1 tank with an Australian Rainbowfish?(the rainbowfish is about 2.5-3 inches) and finally, 3.) What kind of insect should I feed them? Thanks for the answers. ^^