That makes sense. I never thought about dimensions rather than gallons.It does. It absolutely needs to stay at 1.009 or the clock starts over, I usually shoot for 1.008 to play it safe. Make sure you use a refractometer not a hydrometer to measure it. Be sure to calibrate it every day.
SWF says 75 gallon. That is too small. Live Aquaria says 125 which is more reasonable. 220 is better. It is the dimensions not the gallons that matter.
I have a 120 but because it is only 5’ long there are some fish I can’t keep but could in a 125 which only 5 gallons more but is 6’ long.
I ordered a refractometer that will be here in the morning. I started taking the salinity down a bit to 1.018 make sure they are breathing a little easier, just to be on the safe side. But my gauge doesn't go down to 1.009, so have a refractometer being overnighted. Then I'll finish taking it down and be ready to keep it down. The fish are behaving normal still and actually are eating well