I have a few solutions for you
1. what I did on my first reactor (one made out of a gravel vac) is take a 2" to 3" rubber coupling and set the reactor upright in that. I had to cut out a chunk out of the bottom of the coupling so the L that the elbow made could poke out with it standing up.
an example of the coupling can be seen here
2. on my latest reactor (the one I just posted) I create a upside down U by connecting 2 elbows. Ironically enough this creates the perfect hook over the side of an aquarium. I then just make sure to clamp down all the hoses that have weight on them (I normally clamp down any hose outside the tank) and let the weight rest on that reverse U.