You could use two circulation pumps at one end and the filter at another end
Try a rock quarry for the rock that you want, I personally don't know what kind would be best though. They usually charge pretty low and have a BIG selection.
i've been, the biggest problem is that 95% of the rock in quarries here is limestone, which i do not want in my tank. that and well the ones in the area do not have rocks that are a slab that can be cut to work as i need it to. the only rock they have that isn't limestone is the river rocks which again doesn't give me the smooth cut slab i want
i would pull a page from the saltwater guys, drill the back of the tank and run your pipes/tubing/ext through there. Then either use the canister filter or a closed loop system with a pump. When looking at how to make a tank cleaner and have less equipment seems saltwater is way ahead of freshwater for the most part. They've already been there did that.
i could drill the back and then run a hose to the front of the tank, that would eliminate the hose hanging down the back of the tank, and the need to secure the hose under the substrate...
i want to stick with two canisters, i found these loaches to be sensitive water fluxuations in quality, esp ammonia spikes, and i want to minimize losses. would the syphon still work okay with the intank about the output?