So I am a new brewer and have a 6.5 gallon carboy, and I think a 7 gallon bucket. Not knowing that I would have to use yeast starters to up the yeast in order to ferment these bigger batch sizes I tried to go for larger tanks than the standard five gallon. As I am not an electrical expert and my building of my yeast stir plate to compliment a yeast starter is slowed until I can figure out how to use the wire connectors. I am not Bob Vila but I hope to be one day. My question is if I ferment a five gallon batch in these larger vessels are there many downsides? I have heard it will affect the beer and taste. Any thoughts?
For primary fermentation, these are fairly typical bucket & carboy sizes. Once the fermentation starts, you'll start generating CO2 which blankets the top of your beer as it is more dense than oxygen. This prevents the oxidation process which causes the stale cardboard flavor to appear in your beer.
You may want to purge these sizes with CO2 if you plan to use them for secondary fermentation. You don't have the advantage of high CO2 output during the secondary so you're at a higher risk for oxidation with a large headspace.
Active primary fermentation should produce enough CO2 to push all of the oxygen out of the headspace of a large bucket. It may become a concern if you're transferring to a secondary where there will be little activity and potentially not enough CO2 to purge the headspace. Some people are concerned that large secondaries can lead to oxygenation for that reason.
edit: Got distracted and was typing slow so I was a bit late on the answer here.
Are you brewing 5 gallon batches?
Who told you it would effect the beer and taste? There isn't enough space to cause any problems.
I suppose if you were fermenting 3 gallons of beer in a 55 gallon drum there might be something to that.
Most people use a 6.5 carboy so they have plenty of headroom for the krausen.
Thanks for all the tips guys. ^ yes I am brewing 5 gallon batches to match this commercially bought yeast until I become the yeast expert. I am brewing mostly Hefes so I wouldnt really be using a secondary, but when I need a secondary you are telling me I need a five gallon ay... this brew business is sure getting expensive.