Shovelnose might eat the ropefish I don't know.
GARfield is just over 12 inches the ropefish are 12 inchs the sens birchir is 5 inches and the comet GF is 5 inches.
That said, GARfield did take the two front fins off the sens and they grew back, hasn't messed with him since. took the tail off of the comet, it to has grown back and he hasn't messed with him since.
So far GARfield hasn't bothered the ropes and they are in his face when they aren't trying to get out.
I've seen ropes kept with that exact stock and it worked out very well. As long as you get a larger rope I feel it will work, they are escape artists so I doubt they'll get eaten