Is this okay for a single fantail?

[Dangerdoll]

The problem with putting 2 goldies in a 29 gallon isn't the size of the tank, it's the margin for error. There is absolutely no margin. If one thing goes wrong with the tank, it is a devastating problem. My suggestion would be to stick with 1.

 

[InR reason]

Thanks for the info Chil!

I did know that even the single fish would be pushing it, no way would I be getting 2! I've done some more reading and have seen a few sources saying fantails can get larger than the 6"-8" max size if given a larger living area. This makes me hesitant to stuff one in a 29 gallon tank only 12" wide. I have some thinking to do and maybe some furniture to move around to see if I can manage anything larger.

You're being nuerotic. I have 3 fancies in my 29 with great filtration and I'm always on top of WC. They are fine, as our their water parameters.
You'll be fine with 1-3 fancies in a 29g, and I highly suggest you not keep him alone with all that space. I'm sure you'd invest in an oceanarium at this point but in all honesty, you're letting people screw with you.
I've been at this hobby for a while and I've seen some pretty strange stuff. You have to use common sense and research and then make your OWN decision.