For Calcium and Alkalinity (2 part)? Not sure how reliable regular timers would be but maybe others can chime in. You may just want to put that money towards a used controller...
I think I'd at least get a Reefkeeper lite.....only seems like overkill when you compare to a single timer. It does so much more (and does timers so much better) that it's totally worth it.
For perspective, when I initially set up my system I only had plain power strips and appliance timers.
By the time I had my lights (two timer) heaters (one) pumps (two) and whatnot hooked up and accounted for dead timers I'd spent way more than $120 on all the strips, cables, timers, etc.
Now I have extra protection for my heaters, a standby mode for the skimmer (or anything else I want), wave maker timers, etc, etc, etc....in addition to my dosing timers. (I did end up replacing my DIY dosers with a Jebao 4-head.)
So the cost is at least situationally justifiable.
Another option (that didn't exist when I set up) is these programmable WiFi outlets you see by WiON (Woods), Belkin and others. Way cool, but I doubt any of them will cycle on/off in anything less than a whole minute.
Reef keeper Lite is the way to go IMO.....maybe save up for one, or keep your eyes open for a used one?