You can still use it but the "recommended" tank range is due to the gph
it puts out and keep in mind that products like the Tunze, Seio, and Hydor Koralia all put out wider streams of flow versus concentrated streams like the Maxi-Jet ph do for example.
Because of this wider flow IME a higher then usually gph
pump should be used. If interested in the Tunze pumps (and you don't mind spending the money) then a Tunze Turbelle Stream Kit
would be an excellent choice for your tank. They include pumps and the controller to create random currents that more simulate nature.
The Tunze Turbelle Nanostream power heads can also be controlled but typically are best for tanks <100 gal
The higher gph
Seio pumps can also be put on a controller
The Hydor Koralia power heads don't have a controller yet and are best not turned on/off. (Full review with videos
Really it just depends on what you are looking for (wave/steady flow) and how much money you want to spend.