Run the window shaker AC unit!
Unless you're going to vent the chiller outside, the ambient heat from the chiller and the wattage for both the chiller and the pump (especially a genx 40) required to run it will definitely be a waste of energy for a 20g tank...
Yes. Educators and or Penductors have been around for a long time. The reason you don't see them very often is the need for a high pressure rated pumps to get the most bang for your buck out of them. They were big in the hobby back in the days of external pumps like the Iwaki MD series pumps.
They work on low pressure rated pumps but they work extremely well on higher pressure...
The Red Sea kit I used long ago was way off. I always trust my salifert kits. Haven't had an issue in 20 years. There was a time 10+ years agothat people had problems with but I missed that batch. If yours is not expired, I'd trust it.
Treefitty😬
Seriously though, it all depends on what kind of shape they're in. If they are pristine, without any hardware and they're xr30 pros $350 is a good range...
If both kits read the same or close then I doubt they're bad. Fwiw, I have had great success with salifert.
Time to start manually dosing ca/alk/mg on a regular basis....
It's surprising how much alk a maturing tank will go through weekly and or daily. I agree though that it sounds likes bad test kit. Is it a Red Sea kit?