Everyone certainly is entitled to their opinion, but it has been proven through many spectral analysis tests that T5s start to shift their output spectrum around 12 months.....and from the read I remember......that was with ATI bulbs which are some of the best. If trying to maintain a reef with SPS, 9 months is the recommended change point. Certainly does not mean one has to do that. But the optimal T5 change point is certainly before 18 months. So, I guess it would come down to a discussion of what is acceptable vs what is best.
I totally agree with you on API test kits. They are fine and economical for normal testing. When there is a problem, I certainly would not rely heavily on them. But, to get an idea of Ca, test for any detectable PO4 or NO3.....or even NO2 or NH3 for that matter......they are a much more wallet friendly and mostly reliable option. Their copper test kit is just garbage for practicality purposes. I also have Salifert or Red Sea kits to verify...... periodically.......that the numbers API gives me are close. So far, they have always been. Salifert is the only test kit that has ever failed me so bad that I actually harmed livestock........but that was about 4-5 years ago when they had several batches that were found out to be bad. Typically, they are very good.
