Very interesting set-up comparing strains and rearing temps. Higher Nitrate at higher temps is normal due to increased metabolism. My question would be; is it better for the tadpoles physiology to grow fast? All life forms have so much life to live and burning the oil up does shorten it. It might be better for the species; but what about the individual?

A tip for you is that some of the API (and other brand) tests can be conducted with half the volume and thus extend the test kit life x2. For example, the nitrate and ammonia tests require 5 ml. test water and 10 drops each from 2 bottles. With an accurate 1 ml. calibrated dropper or pipette you can measure 2.5 ml. of test water and then half the drops to 5+5. Good luck !