The social media page flagged the clip as containing offensive material, and Rex Goldsmith has branded the process "bizarre".
He told the BBC: "I totally understand censorship - but when you think that Instagram is owned by Facebook, and if you look at some of the videos on Facebook, they are disgusting - some are violent, some have foul language - I find it a bit bizarre that they can then think a bit of cod fillet is offensive.
"It's kind of backfired - if you're scrolling through your Instagram feed and you come across a censored image, you'd want to have a look."
Meanwhile, Instagram's parent company has confirmed the content was mistakenly flagged.
A Facebook spokesman said in a statement: "This content was marked as sensitive in error and has now been reinstated. We apologise for the mistake."
Goldsmith said he has no issue with vegetarians or vegans, but insisted he needed to use the social media platform to advertise his business.
He added: "I can put a video or photo up of a particular fish, and I'll often get direct messages or phone calls saying 'save one for me' - it's a good connector.
"I have nothing against people who choose not to eat meat or fish, but it's my little business and I am precious about it."