Oceanic & Coralife Biocube 29 29G Quality Replacement Cooling Fan - Plug & Play

It will fit nicely on your Oceanic BioCube 29G hood, plug and play, without any modification needed. NOTE: The fan thickness is 0.50". Due to the fact that the hood original fan thickness may vary, you may need shorter or longer screws to accommodate the thickness of this fan.

eBay