I want the tank to tell me when my reservoir is low, but don't wake me up if its after bedtime.

The program below uses a "dummy" timer.  A dummy timer is one which is configured in the AC but is not associated with a real address (e.g., don't assign it to a DC8 or other 'real' device); I traditionally use addresses out of range for the direct connect and other Neptune accessories (e.g., N01-N16, P01-P16)

DAY&-N01

// The dummy timer named DAY is on during the day (8am - 8pm in this example)
If Time > 08:00 Then DAY ON
If Time > 20:00 Then DAY OFF

// SwitchA1 is used to tell when the water is low (you may be using a different switch depending on your configuration)
If SwitchA1 OPEN Then ROT OFF
If SwitchA1 CLOSED Then ROT ON

// Initialize the ALM (alarm) to OFF
If Time > 00:00 Then ALM OFF

// If the ROT (indicted by the switch) is ON then my water is low
If Timer ROT = ON Then ALM ON

// But if it isn't daytime then don't wake me up
If Timer DAY = OFF Then ALM OFF

This is a slight variant from above.  In this example the ALM is only turned on 1 minute every hour rather than continuous.  I use this type of alarm in my tank to indicate a warning rather than a critical condition.

// This uses 2 dummy timers, 1 to indicate daytime and another to control the warning alarm (1 min every hour)
DAY&-N01
AL2&-P06

// The dummy timer named DAY is on during the day (8am - 8pm in this example)
If Time > 08:00 Then DAY ON
If Time > 20:00 Then DAY OFF

// SwitchA1 is used to tell when the water is low (you may be using a different switch depending on your configuration)
If SwitchA1 OPEN Then ROT OFF
If SwitchA1 CLOSED Then ROT ON

// Initialize the ALM (alarm) to OFF
If Time > 00:00 Then ALM OFF

// AL2 on 1 minute every hour, but turn it OFF at night
OSC 001/060 ON/OFF Then AL2 ON
If Timer DAY = OFF Then AL2 OFF

// If the ROT (indicated by the switch) in ON then my water is low and I turn on the alarm (ALM)
If Timer ROT = ON Then ALM ON

// but since this is the warning alarm I turn ALM off if the AL2 timer isn't on
If Timer AL2 = OFF Then ALM OFF