I try to do 10-20% monthly on all my tanks.
For that tank I was dosing Kent Parts A/B with Kalk. I am a huge fan of kalkwasser. Kalkwasser needs to be slowly dialed in but is very effective when mixed with top off and allowed to settle prior to adding to the tank.
With that tank I just stuck a larger piece of foam under the over flow on top of a bag of charcoal. In my new JBJ I am using the media baskets for phosguard, foam and charcoal.
At one point I had a CPR fuge HOB in the center compartment, the fuge while cool did not prove to be of any significant benefit to the tank.
Your tank is looking awesome, the tank has come along way in a short time.