try to limit my lights to 8 hours or so
Are they not on a timer? Consistency, stability, and balance are all key to a healthy, long-lived tank.
I am using two AI Primes, one freshwater and one made for reef aquariums. Neither light goes over 50 % intensity at its highest point.
Those are capable of A LOT of light! Good thing you have the intensity throttled
One thing I did notice is that after posted this, I tested again about 8 hours after the 5ml does, and nitrates were back to around 5ppm which is what it was before I dosed. I doubt the few plants I have in there consumed the additional nitrate so I am leaning towards my testing kit not being properly shaken/stirred up.
The 5ml dose should
have added 1.25ppm NO3. So if we forget about your test shortly after of 20ppm and just see it was 5ppm before, you add 1.25ppm so the total should be 6.25ppm (all things equal), and then you test and read 5ppm. The difference between 5ppm and 6.25ppm with the API liquid is impossible to tell, so in the end I think those two make sense.
The 20ppm test is the odd one. I've read often that timing of the test matters and it's best to let things "settle", but I'm no scientist so I don't really know what's going on.
I will continue to monitor this and do some more testing to confirm. I was also thinking on getting a different nitrate test kit. Ive read get reviews on the Seachem, and Salifert kits.
Anyone have any experience with either of those?
I binned the API NO3 and went with the Salifet NO3. Haven't looked back since!
The one thing I will say is that I went through my first (and only so far) Salifert kit relatively
quickly. I don't think the average hobbyist would notice, but I'm normally running between 5-10 tanks, so my use can be more on the higher end.