The issue with ABS is the reliability of glue bonding of the fittings to the pipe. ABS glues DO NOT actually solvent weld the fittings to the pipe so it is possible for the connections to pop if stressed.
If you look closely at PVC fittings you will find fittings that satisfy the Schedule 40 pressure pipe standard and these fittings have almost twice the surface bonding area as the fittings that are held in seperate bins for what is called DWV applications.
It can be complex to switch from ABS to PVC when you try to use valves and other fittings.
The only place I used ABS fittings in my big pond install was in the bottom drain cones of the sedimentary vortex and the media chambers. And all those lines were encased and reinforced with concrete. All of the primary flow piping was constructed with PVC and good solvent welded joints.
Here is a link to a diagram showing the chambers and their incoming valve plumbing:
http://www.koi-bito.com/forum/100832-post10.html