I'm running a 40g puffer tank (with LR and sand it's more like 30g) for my green spotted puffer and a 10g LR, sand, worms and clams, lol, but my coralline is coming in for both tanks, cyano has been a problem in my puffer tank, but he's been grazing on it and it's almost gone. I can't keep a clean up crew in puffys FOWLR because he eats them all, lol, and as far as keeping a skimmer- No and No.... However I have 60lbs of live rock and 4 inches of sand in my 10g and close to 150lbs live rock and 2 inches of sand in my 40g. I have pristine water and I don't have do to too much (especially in my puffer tank). Macroalgae is a wonderful relief from nite problems, when used to proper way. I actually am surprised at how having my puffy in a starting out reef tank would LOWER my cost and time spent on pwc. Long story I know, but, hey, I'm not running a skimmer on either tank. My puffer tank is established, fully cycled and stable and has been since July (except for a phos spike- algae fix at the end of a nite cycle= problems) and my 10g was waiting for a little while but now has more rock and quite quickly going coralline as the cyano dies off- levels on this tank have been pristine for 9 days now- YAY!!! I do agree if it's not a nano or pico or a planned eco-habitat a skimmer is a good investment.... In the same breath I will never buy one, and PWC should be my middle name lol.