it should be more than enough.....i have 2 in my 300 and have to keep them under 100% otherwise the sand is moving all over. For reference, the dimensions of my tank are 72"x30"x30"
4 ft or 5 ft long? You have sand? One provides plenty of flow, although two would be better and provide more random flow options. I have two on my 4x2x2 120g
I got 2 on my 3ft 65 gallon. They go up to 80% at times. It is a sps dominant tank. I started with 1 but wanted more flow or back and forth flow. Gteat thing with them is you can by 1 then when you need it buy a pump only and add it to the controller
I would recommend two. I have a 90 gal (36 x 24 x 24) and I have two of the XF 230's. One Gyre may be enough for your tank but with two you have many more flow pattern options and with the importance of flow for SPS I would ALWAYS suggest that more is better.