They 19-year-old secured a two-year deal with the League Two outfit after training with them throughout the summer.
His only appearance so far for The Red Devils came in the EFL Cup defeat at Exeter City earlier this month.
Previously, Fish was a product of the Leyton Orient Academy and signed his first professional contract at Brisbane Road in 2022.
He spent some time on loan with Bowers & Pitsea in the Isthmian League Premier Division last season, scoring 3 times in 14 appearances.
With Greg Luer sidelined through injury and Jake Robinson still nursing his way back from a long lay off, the Welsh under-18 international arrives on a one month deal to provide manager Adam Hinshelwood with another attacking option.
It continues a growing relationship with our close neighbours which has also seen Davide Rodari and Mo Shubbar gain first team experience with loan spells at Woodside Road in recent seasons.