Larger fermenter than necessary

[Svenhook]

Currently all my equipment is 5 gallon sized. I was considering making a 5 gallon batch and splitting it into two 2.5 gallon batches so that I can experiment with one and compare. Is there any issue in using a 5 gallon fermenter for only 2.5 gallons of wort?

Thanks!

 

[Revvy]

5 gallon is about the biggest I would go, and have gone, with 2.5 gallon batches. Though I really try normally to have no more than a "gallon" worth of headspace in my fermenters. You can go with 2.5 in a 5 if you have no other options.