I haven't created a yeast starter before but I've been doing research on one and was wondering if i am making a 1 liter or 1 gallon yeast starter, to i reduce the total wort and water in the carboy to have a final volume of 5 gallons or do i still make the normal 5 gallons and just add the yeast starter on top no matter what the size?
The second way. Oftentimes, you can refrigerate the starter for 12 hours, which will help settle the yeast on the bottom, and you can pour out most of your spent starter liquid, reserving just enough to swirl and re-suspend your yeast before pitching.
What Nathan said second. If your starter is over a liter (and sometimes even less) it's not a bad idea to chill the starter for a day or two in the fridge prior to brew day. The yeast will drop and settle, allowing you to gently pour the liquid off the slurry, leaving only enough to swirl the slurry and pitch that. Because honestly, with a 1 gallon starter, do you want a full 20% of your beer being a different "recipe", unhopped, and likely highly oxidized (especially if you used a stir plate or frequent agitation)?
