20gal Questions.

[JasonJ]

i have an extra 20gal tank.
i was wondering if the 24" corallife aqualight 130 watts PC is good enough for it. im planning go get at least 25lbs of LR, couple of PHs, AC powerfilter, 1-2 inch sandbed, cleanup crew, a shrimp, 2 clowns, some zoos, softies, and a RBTA. just doing the basic stuff...still learnin and readin. goin to do everything reallllllllyyy slowww. for water changes i could buy pre mixed water from my LFS. i was wondering if this is a good idea? since i dont want to spend money on a R/O unit. the thing is the water is from their main system that holds cured LR. its $5 per 5gal of premixed water. do i need to run a skimmer? if so im goin with the remora brand..but that will be later on down the road...since money is tight coz of school. any other suggestions are welcome.
thanks in advance.