First of all great set-up! Awesome rays!
Second this is great advice. Jap mat is awesome media and the poly wool will make the water sparkle. As for the ph I don't think it'll be an issue. My ph is 8.0-8.2. I have an automatic drip system that changes out 50 gallons/day. I also have chloramine in my water. I found out, quite by accident, that even if the dosing pump fails the system will absorb the the ammonia and the chlorine will dissipate. I went away for 14 days to work and came back to find the dosing chamber just as full as when I'd left.(both check valves were clogged). I have a mardel ammonia alert on the tank which reads as low 0.02ppm. It has replaceable cartridges so I thought the cartridge must be old and therfore not reading anything. I replaced it with a new one and still read 0ppm ammonia.
All of the fish were fine. The tank is a 230 gallon with a 33 gallon sump with a bio tower. Tank has 2 small pearl x motoro rays, a super red arowana, 10 5-7" clown loaches, 2 synodontis cats and 2 plecos.
Would I recommend a drip system without a dosing set-up? Not in a million years, but it can be done, obviously. If i had some cheaper fish I might try it.

As long as your media is well established and the amount of water entering the system is slowly introduced over a 24 hr period there shouldn't be any side effects.
Problems could arise if you tried to do this on a once a day set-up if all of the water was changed at once. Too much chlorine and ammonia, chloramine, would certainly have toxic effects.
Your system seems pretty sound and your fish look amazing. I just thought I'd share this info so you don't have to be constantly worried about your water parameters as I used to be. There is actually more room for error than most people think when you are set-up on a drip system.