Hi
for 24" deep tank you 100% dont need optics with the metis unit, we have clients running these on 30" deep mixed reef, however if you personally feel you need optics which would really detract from the design and development of the fixture, yes they can be fitted at a price as a custom unit.
You maybe reading the PAR readings wrong, the distance refers to the fixture height above the water line
We had 60 degree optics fitted to a tank that was 6 feet deep for obvious reasons so to apply the same optics to 24" is really not a requirement.
