well, im not sure... it may be OK in a 26 gallon. I think they are generally reccomended for 40+ gallon tanks, but if you dont want many other corals, and realize the fact that it will get rather long, and walks as well as stings other corals you may be ok. Im looking into eventually putting one in my 110g tank to host a clown, or maybe a pair.
If you are willing to take that hit, and can take care of the water, than you may be ok. You can buy them very small as well, like 1-2" and then it should take a while to get large.