Dimmable t5 ballasts use 0-10v pwm to dim. But regular electronic ballasts can not dim.
With t5/led hybrids i would do 1 of 2 options.
1 have leds ramp up and down.
Right before they plateau have t5’s switch on a little after sunset begins have t5’s off. Still get ramping, less money, can use aquatic life fixture, dont have to build housing.
2). Dimmable ballasts hybrids usually come with their own leds. These are also really expensive i think the ati one for 4’ is like $2000.
What i was looking at was 2 of these.
https://www.bulkreefsupply.com/dimmable-t5-ho-miro-4-retrofit-kit-let-lighting.html
To compliment 4 ai primes.
Inside a frame of aluminum corner trim rectangle, with trim parallel inside to hold the leds. Paint black.
For whenever i actually upgrade to a 4’ tank anyway lol.