Well, that was completely unsuccessful. My hose only outputs 5 g/m, which means after a little over 4 hours I only exchanged 1300 gallons of water. Because the rate was so slow, and the relative temperatures pretty close, I think I was getting much more mixing than I anticipated. Results:
Before:
FC/CC: 8.0/0
PH: 7.8
TA: 80
CH: 400
CYA: 70
After:
FC/CC: 6.5/0
PH: 7.8
TA: 90
CH: 400
CYA: 70
Had I actually exchanged 1300 gallons of water, I should have ended up with a CH of 350 (given my tap CH) and a CYA of 60. Even then, I'd be a long way from my target CYA of 40, which would let me do my daily testing with the OTO vs. the FAS-DPD. Oddly enough, the FC drop was withing 0.5 of what I expected (our tap water has an FC of 1), but maybe some of that was due to the pump, weight, hose, etc.