Hello Pogipoints,
Welcome to Reef Sanctuary!
If you have the C-250 like I do you're going to want to order two of the Innovative Marine Spin Stream nozzles. You can purchase them from your LFS or make an online order at Amazon, Marine Depot, or
Bulk Reef Supply.
The kit will include adapters and one will fit over the stock nozzles on the C-250. However, this might make your output a little long so I suggest you cut it slightly shorter to make it more snug with the nozzle. I used regular undersized vinyl tubing and boiled the ends to ensure a tight fit and worked them over the nozzle and the spin stream.
I'm using 60 pounds of Fiji Pink and have zero sand movement in relation to the Spin Streams after installing them.