first time with salt i have a rimless 4 gal tank 10 pounds of live sand 5 pounds of live rock 18w t5 getting a nother 18w antic t5 would a ac20 be enough flow at 100 gph if i used it as a refuge or what ever they are called all i want is a pistal sheimp and yellow watchman gobby and some starburst coral i think its called would that work with weekly water changes? plz let me know