Everything I can measure is good, why will he not eat?

[Grey]

I've had this axolotl for a few years, but recently moved to a new house and he's stopped eating. I'd expected a bit of change-related stress, but it's been a few weeks now and I'm getting worried. He's very active (swimming around more than usual) and his gills are a bit more forward-curled than I like to see, but otherwise I can't see anything wrong with him or his setup.
pH: 7.6
ammonia: 0
Nitrite: 0
Nitrate: 20 (coming up on water change time)
water temp: 70
light: low
water movement: not much
substrate: same sand it's always been
I don't get it. Any idea what's wrong? The only thing I can think of is there's ~something~ unsatisfactory about the well water here, which would be a bummer because there's not much I can do to change that so I'd have to give him to someone with better water

 

[AMurry24537]

I would suggest lowering the temperature by several degrees; 70 is right on the edge of dangerous territory and it's really easy for it to go up. I personally usually aim for 63-65.

If your previous temps were also the same, I would guess that you're right about it being something in the water. I would suggest testing out how hard the water is (this is related to, but not the same as ph) as that can cause issues. Is the end of the tail curled at all? You could try using spring water as an alternative source.