Just remember, some people dont agree, but skimmers for a tank bigger then yours will be bad because it will over skim the good nutrients outta your tank
if you feed your fish good you won't overskim. calcium,alk can't be skimmed out and daily feedings and regular w/c will replenish. I wouldn't worry about over skimming any tank unless the skimmer is grossly overrated for the tank= 40g with an aerofoamer 830
