Unless you're going with the Walstad method with high plant bio-mass and low-fauna mass as well as next to no fertilizing, then you don't need water changes.
In all other cases, it's good to have (shrimp tanks aside perhaps). Change out 20% and if you follow a heavy fert regime (which is doubtful considering your low light range), then move to 50%.
Water changes don't hurt nobody.
You're not going anything wrong and this isn't some single point of failure issue. You'll be fine!