Here's my latest update. Apparently, I had 7.0 & 10.0 buffer solutions - recalibrated using the 7.0. Used the liquid test to test tap water which was at 7.4, meter was pretty close. Then confirmed with tank that was reading 6.4 per API liquid test. On to the tanks (below 6.0) to get readings. One was reading 4.2 (tanks has CRS, PFRs, albino long fin pleco, and plants, aquasoil amazonia) & another read 4.4 (betta, 2 ottos, plants, reg lfs gravel). Is this reasonable and surviving in this low pH? No ammonia, nitrate, nitrite.