It is always about availability rather than residual levels. In the ocean nutrient availability levels are high - even if residual levels show low. Also depending on currents sometimes residual levels also can become high. Also, regarding sps needing low nutrients may not be very true. There are studies/ ancedotal evidence that shows sps growth is higher in higher phospate levels. What sps dont like is instability. So if you go from high phospates for some time to low phospates then that negatively impacts them. Same thing from low to high but to a lesser extent. Interesting discussion thou
You might want to share the placement of your tank.
Also, In my experience I'm able to keep leather corals without chiller.
But considering now I've chiller in my tank, leather do alot better with chiller and faster growth.
So yes, you might be able to do so depending where you place your tank and what is the room temperature.
Do note because you do not have chiller, equipment in your tank also produce heat thus might increase the temperature.
My dream is to have a marine tank with marine critters and softies only. Considering that Softies are thought to be more forgiving to parameters, do I really need to have a chiller for my tank?
Still planning so have to think of the equipment I need to cater for.