1-1.5 lbs per gallon is the rule of thumb. But you don't have to follow that rule. I think the more the better but you should put in whatever amount aquascapes your tank the way you want. Skimmer is not neccesary but once you've used one and seen the difference, You'll get one. Filters definately needed, also use a power head aimed upwards to create a ripple on the surface of your water. This prevents the gases and oils from gathering on the surface of your water. Good Luck !