My Trident only tests Alk four times per day, not six (12am , 6am, 12pm and 6pm).
Not sure why you would throw out Alk reagent when the Ca and Mg are depleted. I will open the drawer and feel how much is in the bottle. Then do a 'reset' on whichever Trident "thinks" is running out so that I can use the remaining reagent. Note that one needs to be careful with this approach so as not to actually run out of the reagent.
There may be an adanced way to program the Trident differently to tailor to your needs. I believe the fellow is @ApexGuy (edit:
@SuncrestReef ) or something similar who has a ton of articles on Apex programming.
Regarding the $200 cost...that is a different story. Hopefully, you can find another resource for reagents.