Hey Juan.
Refugium is running 11 pm - 11 am. Opposing light cycle. I’ve been trying to reduce the nuisance algae in the fuge. Clean it up so that mangroves and sea grass are the major plant life in there. I should stop calling in a fuge since my end goal is to have pipe fish or something similar in there. It’s going to be a secondary display. The ideal deep sand bed has the ability to help filter nutrients, so there is value with that and maybe too much? My system is over filtered as it is. Someday I might remove some live rock from sumps to cut down on the filtering capacity.
Again, I’m trying to be systematic because things are looking good. Just minor tweaks from here.
Air:
The way my fish room is set up, it’s sealed pretty tight. Moisture and heat are trapped in there. That was the intention to protect the house (floor joists, HVAC ducts, etc.). I run one vent fan 24-7 (90cfm) in that room. I have a secondary vent (300cfm) that is controlled by the apex based on aquarium temperature, so it’s my chiller. I also have other fans for evaporative cooling controlled by aquarium temp. They’re staged so that the hotter the system gets, the more fans come on.
Those ceiling vent fans pull air from the room. The only opening in the room is through vents in the aquarium hood. It pulls cool living space air through the hood, past the lights, into the filtration room where it is mixed and eventually sucked outside. All of the cool air in the basement has to be replaced by air coming in from the other side of the house near the HVAC system. The fresh air intake for HVAC are two 8” pipes. I can feel the air movement in those pipes when the aquarium air movement is on full. I also added some vent grates in the walls down there which allows for easy air movement across the basement.
So, I agree, fresh air is a huge benefit. I am hopefully getting a decent amount. I could possibly put on CO2 scrubbers on the skimmer. That’s one thing I haven’t done yet which I used on my last system.