I am not a reefer, but use an AC III to drive a very high tech f/w planted tank. While my code may be different (controlling different systems to different parameters), the principals for coding an AC III should be the same.
I find it helpful to distinguish between something that needs my attention, but is not immediately critical, and those things that indicated a massive problem. So I use both the standard ALM& timer and an additional BAD% timer.
This is just a small sample of code showing how I would use that:
If pH < 06.00 Then ALM ON \\ Small problem that needs attention
If pH < 05.80 Then BAD ON \\ Something has gone very, very wrong!
If Temp < 80.0 Then ALM ON \\ Small problem that needs attention
If Temp > 85.0 Then ALM ON \\ Small problem that needs attention
If Temp > 90.0 Then BAD ON \\ Something has gone very, very wrong!
If Timer BAD = ON Then AIR ON \\Something very wrong, revert to minimal systems
If Timer BAD = ON Then LT1 OFF \\Something very wrong, revert to minimal systems
If Timer BAD = ON Then PM1 OFF \\Something very wrong, revert to minimal systems
If Timer BAD = ON Then PM2 OFF \\Something very wrong, revert to minimal systems
If Timer BAD = ON Then CO2 OFF \\Something very wrong, revert to minimal systems
If Timer BAD = ON Then HT1 OFF \\Something very wrong, revert to minimal systems
If Timer BAD = ON Then UV_ OFF \\Something very wrong, revert to minimal systems
The idea here is that there are some things that need attention - use the ALM for that, and intervene as needed. But other parameters values can indicate that something has gone WAY beyond anywhere they should ever go - indicating that the unexpected (and unknown) has happened, in all likelihood an equipment malfunction of some form. In which case the best course of action is assume the worst, and revert back to the absolute minimal life support until you can assess the situation and take remedial action.
I'm happy to say, my BAD timer has never kicked in. But it's nice to know it's there.
