You might simply use a float valve(or a redundant pair) + a solenoid drain, say a 8-10mm.
Then place the solenoid on a timer, so you have automated water changes and it can take 2-3-8 hours etc.
Drain and fill is slow and controlled by th time the solenoid is open and the orifice sizing.
Smaller/shorter times= less % water removed at once.
So it's a bit up to you how to do this.
Also, with a trickle filter, you can add various plants, like peace lilies etc, and small 15 W FL light and grow many species in the filter itself. Plants are the filter basically.
But unlike the ones in the tank, emergent plants are right next to the light you add and no CO2 issues.
So they just remove nutrients really well. Since the tank is larger, an automated system, or a fast larger valve for draining, and refilling would be a huge help. Add activated carbon prefilter to remove chlorine.
Worth every penny/labor.
I like semi automation, I just turn a 3-5 cm PVC valve to drain the tank, say a 1200 liter, in about 15 minutes to 60% water changes. Then I turn on a 2cm refill with warm water(say 28C), and add dechlorinator and about 1 hour later, after I've cleaned the tank, trimmed, cleaned the filter etc, and watered the lawn, I'm done, so under 2 hours once a week for a rather large tank.
No lifting etc.
Easy.
Regards,
Tom Barr