Heretic!!!! I loves muh bukets!
Seriously I've been brewing for 8+ years and have never seen my beer fermenting. In those 8 years I've also never had a problem knowing when my beer is fermenting and have removed the lid prior to thinking fermentation was complete less than 5 times on the better part of 100 batches. If its a problem for the OP/others, sorry, just not an issue here. Good luck.
Seriously I've been brewing for 8+ years and have never seen my beer fermenting. In those 8 years I've also never had a problem knowing when my beer is fermenting and have removed the lid prior to thinking fermentation was complete less than 5 times on the better part of 100 batches. If its a problem for the OP/others, sorry, just not an issue here. Good luck.