I don't know about Omega-3 fish oils specifically as a treatment for pouchitis, but there have been some studies which suggest fish oil has a positive impact on Crohn's (in combination with other things, of course). In general, Omega-3s may have anti-inflammatory properties, so theoretically there may be some benefit to taking them when you have pouchitis.
Of note, for past 3.5 years I've been talking turmeric and Align. I was already taking Omega-3, vit-D, calcium, and magnesium along with multi-vits and iron before that so I just added them to my daily regime (lots of pills, I know). I have not required antibiotics since 2012/2013, and my last scope in July of this year showed a "perfect" and very healthy pouch. Obviously there is no way to know for sure if the turmeric and/or Align is what has kept pouchits in check for me during this time, but I do feel my pouch function has overall been better since I've been taking them regularly. That said, my pouchitis had already been treated and was in remission (subclinical) when I started this regime. In general, there is little clinical information to suggest that probiotics or other remedies are in any way effective for active pouchitis cases, so if you already have full blown pouchitis, anything other than antibiotics may be ineffective in putting it into remission.
Some people apparently do have luck managing pouchitis with Pepto-Bismol, I think 2-4 tablets taken daily, but I don't think there haven't any studies on its long term effectiveness as a treatment, and from what I have read on these boards in the past, there have been isolated reports of cognitive side effects as well as GI bleeding after prolonged use. Jan perhaps has more information about Pepto and can provide more insight on its use for pouchitis and any side effects.